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Category: Medical sciences and health

• medicine
• immunology

Immunologic reactions 

 

The Gell and Coombs Classification of Immunologic Reactions serves as a foundational framework for understanding immune-mediated reactions, though it's important to note that it doesn't encompass the entirety of complex immune processes. This classification system categorizes immune reactions into four main types, each characterized by distinct mechanisms and clinical presentations.

 

**Type I: Immediate Reactions (IgE Mediated)**

 

In Type I reactions, the immune response is triggered rapidly upon exposure to a specific antigen. This interaction results in the cross-linking of Immunoglobulin E (IgE) antibodies bound to mast cells and basophils. This cross-linking initiates the release of inflammatory mediators, including histamine, leukotrienes, prostaglandins, and tryptase. The immediate release of these substances can lead to symptoms such as urticaria (hives), angioedema (localized swelling), rhinitis (runny nose), wheezing, gastrointestinal distress (diarrhea, vomiting), hypotension (low blood pressure), and in severe cases, anaphylaxis. It typically occurs within minutes of antigen exposure. Late-phase Type I reactions can also manifest, causing symptom recurrence 4 to 8 hours after exposure. Clinical examples encompass allergic conditions like urticaria, allergic rhinitis, insect venom allergies, and various drug or food allergies.

 

**Type II: Cytotoxic Reactions**

 

Type II reactions are mediated by antibodies, predominantly IgG and IgM, which target specific cell surface or tissue antigens. These antigens can be of native, foreign, or hapten nature (small foreign molecules attached to larger native molecules). Antibodies in Type II reactions can destroy cells through opsonization (coating for phagocytosis), complement-mediated lysis, or antibody-dependent cellular cytotoxicity. Clinical examples include conditions like penicillin-induced autoimmune hemolytic anemia (directed at cell surface antigens), Goodpasture disease (directed at tissue antigens, specifically basement membrane components), and myasthenia gravis (directed at tissue antigens, particularly the acetylcholine receptors on muscle cells).

 

**Type III: Immune Complex Reactions**

 

In Type III reactions, exposure to antigens, especially in genetically predisposed individuals, leads to the formation of antigen-antibody complexes. These complexes activate complement and attract neutrophils, resulting in tissue inflammation. Commonly affected areas include the skin, kidneys, joints, and the lymphoreticular system. Clinically, Type III reactions often present with symptoms resembling "serum sickness," which typically occurs 10 to 14 days after exposure. This type of reaction is often associated with the use of β-lactam antibiotics or nonhuman antiserum, such as antithymocyte globulin or antivenoms. Clinical examples encompass conditions like serum sickness and immune complex-mediated vasculitis.

 

**Type IV: Delayed Hypersensitivity Reactions (T-Cell Mediated)**

 

Type IV reactions are T-cell mediated and typically involve the activation of sensitized T cells, particularly CD4+ cells, upon exposure to an antigen. This activation leads to tissue inflammation, but unlike Type I, the response is delayed and typically occurs 48 to 96 hours after exposure. Clinical examples of Type IV reactions include allergic contact dermatitis, often seen in response to substances like poison ivy, and tuberculin sensitivity tests, which are used to diagnose tuberculosis.

 

In summary, the Gell and Coombs Classification offers valuable insights into the diverse ways the immune system responds to antigens, providing a foundation for understanding and categorizing immune-mediated reactions, although it is not an exhaustive representation of the complexity of immune responses.

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Category: Medical sciences and health

• medicine
• symptoms
• gastrointestinal

Nausea and Vomiting

 

Feeling sick to your stomach and throwing up can happen for various reasons. In some cases, it might be due to stomach or liver problems, bleeding in the upper gut, slow bowel movement after surgery, or serious brain issues. If you experience long-lasting or recurring nausea, vomiting, and tummy pain, it could be linked to digestive issues causing your stomach or small intestine to get partially blocked now and then. When these symptoms continue without tummy pain, it could be because your stomach doesn't empty properly or your small intestine doesn't move as it should. Other causes could include medications, pregnancy, brain problems, heart issues, hormone imbalances, ear issues, mental health problems, or eating disorders like bulimia. Sometimes, unexplained nausea and vomiting can happen due to a condition where specific cells in your stomach aren't working right, similar to what occurs in gastroparesis. If you vomit undigested food hours after eating, it could mean you have a blocked stomach or gastroparesis. If you have a swollen belly or throw up material that looks like poop, it could be a sign of a small intestine blockage.

 

Nausea is that unpleasant feeling you get when you might throw up soon. Vomiting, on the other hand, is when your body forcefully pushes out stomach contents, involving squeezing muscles in your stomach and chest. The reasons for feeling nauseous and vomiting can be different, but it's helpful to look at how long you've been dealing with these symptoms and whether you have stomach pain.

 

If you suddenly start vomiting with severe stomach pain, it could be a sign of a severe issue that might need surgery. This could include problems like a blocked gut, blood flow issues in the intestines, inflammation of the pancreas, gallbladder pain, or conditions causing stomach lining inflammation like appendicitis or a torn gut wall. If you're vomiting without stomach pain, it's often linked to medications, motion sickness, or other factors.

Diagnosis:

In most cases where someone is throwing up suddenly without stomach pain, it often gets better on its own and doesn't need special testing. However, it's important to rule out vomiting caused by medications or pregnancy. If the vomiting is severe, the doctor might check your blood for electrolyte levels to make sure they're normal. High blood sugar can lead to a condition called acute gastroparesis, which slows down digestion. If your liver or pancreas isn't working as it should, your blood tests might show that. 

 

Now, if someone has both stomach pain and vomiting, the doctor might do an abdominal X-ray or a CT scan to see if there's a problem in the digestive tract, like a blockage or a tear in the gut, or an issue with the pancreas or liver.

 

But when someone's been vomiting for a while and it's not clear why, doctors want to figure out if it's due to a problem in the digestive tract, issues with how the digestive system moves things along, or something unrelated to the gut. To do that, they might suggest tests like a scope exam of the esophagus, stomach, and small intestine, special X-rays of the gut, detailed imaging of the abdomen, tests to see how well the gut muscles are working, or even scans of the head to check for brain problems.

 

 

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Category: Medical sciences and health

• medicine
• cardiovascular
• chest

Chest pain can have many causes, but it’s often linked to heart problems. This pain can vary from mild discomfort to severe and may signal a heart attack (MI), unstable angina, or aortic dissection. However, it can also be due to lung issues (like pulmonary embolism), chest or shoulder muscle problems, or stomach and digestive problems (like acid reflux or ulcers).

 

Heart-related chest pain typically builds up for several minutes and might spread to the neck, shoulder, or arms. It’s important to take any chest discomfort seriously.

 

Doctors use patient history, physical exams, and electrocardiograms (ECGs) to estimate the likelihood of a heart problem. High-sensitivity troponin tests can be very helpful, especially when ECGs don’t provide clear results.

 

Unstable angina feels similar to a heart attack but is often triggered by activity and responds faster to anti-angina medication.

 

Aortic dissection usually starts with sudden, severe chest pain that can spread to the back. The pain’s location can give clues about where the dissection is happening.

 

If someone has back pain or risk factors like high blood pressure, further tests like transesophageal echocardiography, CT, or MRI might be needed.

 

Other conditions, like pericarditis or pulmonary embolism, can cause chest pain too. It’s important to distinguish between these possibilities.

 

In patients with heart disease, symptoms can be diverse, and sometimes there are no symptoms at all. Therefore, it’s crucial to carefully evaluate patients for early signs of heart disease and provide appropriate treatment.

 

Although there has been progress in diagnosing and treating heart disease, it remains a significant cause of death. Regular check-ups with a primary care doctor, especially for those over 65, can reduce the overall risk of death from heart disease.

 

In urgent situations like suspected heart attack, unstable angina, aortic dissection, pulmonary edema, or pulmonary embolism, quick evaluation and tests are essential to determine the problem and start treatment promptly.

Chest discomfort that comes and goes can happen due to various reasons, both heart-related and not. One way to find out if it's related to heart problems is to perform stress tests. These tests can help identify if there's temporary reduced blood flow to the heart muscle (myocardial ischemia) as the cause of the chest discomfort.

 

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Category: Medical sciences and health

• medicine
• cardiovascular
• chest

Palpitations refer to the feeling of having an irregular or unusual heartbeat. They can be caused by various heart rhythm issues, both with and without underlying heart problems. To understand palpitations, it's important to consider factors like how often they happen, what triggers them, and any related symptoms such as chest pain, shortness of breath, dizziness, or fainting.

 

When evaluating palpitations, it's crucial to determine if the irregularity in the heartbeat is constant or intermittent. For instance, a "skipped beat" or a feeling of the heart "flip-flopping" might indicate a premature contraction, different from the irregular rhythm seen in conditions like atrial fibrillation or the fast yet regular rhythm of supraventricular tachycardia. If palpitations are accompanied by chest pain, shortness of breath, dizziness, or sweating, it suggests a significant impact on heart function and requires further assessment.

 

Typically, the evaluation starts with ambulatory electrocardiography (ECG), especially if structural heart issues or severe symptoms are present. Depending on the findings, more extensive testing may be necessary, particularly if there's suspected underlying heart disease.

 

Lightheadedness or fainting can result from various causes, such as heart rhythm problems, changes in cardiac output, vasomotor issues, or low blood pressure when standing up (orthostatic hypotension). Neurological conditions like migraines, transient ischemic attacks, or seizures can also lead to temporary loss of consciousness. Diagnosis often involves a careful history, physical examination, and ECG, which can help identify the cause.

 

Fainting due to a heart rhythm problem typically happens suddenly. Fainting during or right after physical activity might indicate conditions like aortic stenosis or hypertrophic obstructive cardiomyopathy. Additional testing may be needed to determine the exact cause, especially if the initial evaluation doesn't provide a clear diagnosis, particularly in patients with heart disease or abnormal ECG results. Continuous ambulatory ECG monitoring can help identify arrhythmias, and in some cases, specialized electrophysiological testing might be necessary. For individuals without evident heart disease, tilt testing can be useful to detect vasomotor issues causing fainting.

 

AMERICAN HEART ASSOCIATION/AMERICAN COLLEGE OF CARDIOLOGY GUIDELINES FOR USE OF DIAGNOSTIC TESTS IN PATIENTS WITH PALPITATIONS*

AMBULATORY ELECTROCARDIOGRAPHY:

 

- Class I:

  - Palpitations, syncope, dizziness.

 

- Class II:

  - Shortness of breath, chest pain, or fatigue (episodic and strongly suggestive of an arrhythmia if related to palpitations).

 

- Class III:

  - Symptoms not reasonably expected to be caused by arrhythmia.

 

ELECTROPHYSIOLOGIC STUDY:

 

- Class I:

  - Patients with palpitations and documented inappropriately rapid pulse rate when ECG fails to identify the cause.

  - Patients with palpitations preceding a syncopal episode.

 

- Class II:

  - Patients with clinically significant, sporadic palpitations suspected to be of cardiac origin.

  - Studies aim to determine arrhythmia mechanisms, guide therapy, or assess prognosis.

 

- Class III:

  - Patients with palpitations documented to have extracardiac causes (e.g., hyperthyroidism).

 

ECHOCARDIOGRAPHY:

 

- Class I:

  - Arrhythmias with evidence of heart disease.

  - Family history of genetic disorders associated with arrhythmias.

 

- Class II:

  - Arrhythmias commonly associated with no evidence of heart disease.

  - Atrial fibrillation or flutter.

 

- Class III:

  - Palpitations without evidence of arrhythmias.

  - Minor arrhythmias without evidence of heart disease.

 

 

1.Supraventricular Arrhythmias: This term refers to abnormal heart rhythms (arrhythmias) that originate in areas of the heart above the ventricles. The heart has four chambers: two upper chambers called atria and two lower chambers called ventricles. Supraventricular arrhythmias occur in the atria or in the specialized conduction system above the ventricles.

2.Bradyarrhythmias: These are slow heart rhythms. “Brady” means slow, so bradyarrhythmias are arrhythmias where the heart beats at a slower rate than normal.

3.Tachyarrhythmias: These are fast heart rhythms. “Tachy” means fast, so tachyarrhythmias are arrhythmias where the heart beats at a faster rate than normal.

4.His Bundle: The His bundle is a part of the heart’s electrical conduction system. It’s a bundle of specialized cells that help transmit electrical signals from the atria to the ventricles, allowing the heart to beat in a coordinated manner.

5.Supraventricular in Origin: When we say a rhythm is “supraventricular in origin,” it means that this abnormal heart rhythm starts in the areas of the heart located above the His bundle. In other words, it originates in the atria or in the specialized conduction pathways between the atria and ventricles.

 

So, in summary, supraventricular arrhythmias can be categorized into two main types: bradyarrhythmias (slow rhythms) and tachyarrhythmias (fast rhythms). Any abnormal rhythm that starts in the atria or above the His bundle is considered supraventricular. These arrhythmias are different from ventricular arrhythmias, which originate in the ventricles, the lower chambers of the heart.

 

 

1.Ventricular Arrhythmias: These are abnormal heart rhythms (arrhythmias) that originate in the ventricles, which are the lower chambers of the heart. The ventricles are responsible for pumping blood to the body.

2.His-Purkinje Tissue: This refers to specialized tissue in the heart that helps conduct electrical signals, allowing the heart to beat in a coordinated manner. It’s part of the heart’s natural electrical system.

3.Types of Ventricular Arrhythmias: Ventricular arrhythmias come in different forms:

•Premature Ventricular Contractions (PVCs): These are early, extra heartbeats that start in the ventricles.

•Nonsustained Ventricular Tachycardia (VT): This is when there are three or more rapid ventricular contractions in a row, but they don’t last very long.

•Sustained Ventricular Tachycardia (VT): This is a continuous, fast rhythm in the ventricles that lasts for more than 30 seconds and can lead to serious issues.

•Ventricular Fibrillation (VF): This is a life-threatening, extremely chaotic ventricular rhythm where the heart quivers rather than pumps effectively.

4.Definitions of VT: Ventricular tachycardia is defined as three or more consecutive ventricular contractions at a rate faster than 100 beats per minute. Sustained VT is when this rapid rhythm lasts for 30 seconds or longer. Sustained VT can cause severe problems, especially in people with underlying heart conditions.

5.Types of VT: VT can be further categorized:

•Monomorphic VT: This is a fast, wide-complex tachycardia where the QRS complexes (part of the ECG) all look the same from beat to beat.

•Polymorphic VT: In this type, the QRS complexes vary in shape and direction from beat to beat. Very fast polymorphic VT can be hard to distinguish from VF.

•Ventricular Fibrillation (VF): VF is a highly irregular, extremely fast ventricular rhythm where there is no effective pumping of blood. It’s a dire situation.

6.Torsades de Pointes and Bidirectional Polymorphic VT: These are specific subtypes of polymorphic VT, each with unique features.

7.Pleomorphic VT: This is when multiple episodes of monomorphic VT with different QRS configurations occur at different times in the same patient.

 

In summary, ventricular arrhythmias are abnormal rhythms originating in the heart’s ventricles. They can range from premature contractions to life-threatening rhythms like VF. VT can be categorized based on its characteristics, and certain types, especially sustained VT, can have serious consequences.

 

1.Prevalence of PVCs (Premature Ventricular Contractions): The occurrence of PVCs is influenced by how and how long heart activity is monitored. If monitoring spans 24 hours or more, PVCs can be observed in about 50% of seemingly healthy individuals. However, even if PVCs are symptomless, they might indicate more severe underlying heart issues.

2.Nonsustained VT (Ventricular Tachycardia): This is when there are rapid, abnormal heart rhythms that don’t last long. Up to 3% of people without known heart problems might experience nonsustained VT. The likelihood of PVCs and nonsustained VT increases not only with age but also with the presence and severity of heart disease. Therefore, finding nonsustained VT, even incidentally in a symptomless person, often leads to a cardiac evaluation to rule out underlying heart disease. In the late stages of a heart attack (myocardial infarction or MI), the prevalence of nonsustained VT can rise to 7-12%. It can be even higher, around 80%, in patients with heart failure due to dilated cardiomyopathy.

3.Idiopathic VT and VF (Ventricular Fibrillation): Idiopathic VT is a type of sustained VT that occurs without any identifiable heart disease. Idiopathic VF, on the other hand, is extremely rare. Ventricular arrhythmias, particularly VT and VF, are responsible for about 50% of all yearly cardiovascular deaths in the United States.

4.Underlying Heart Disease and Age: The type of heart disease associated with VT and VF varies with age. In individuals under 30 years old, genetic cardiomyopathies are the most common underlying conditions. In contrast, those over 40 years old are more likely to have acute heart attacks (MI) or chronic ischemic cardiomyopathies as the root causes of these arrhythmias. Interestingly, in about 13% of sudden cardiac deaths where there’s no clear heart disease found during autopsy, postmortem genetic analysis can reveal pathologic mutations in ion channels. These mutations, referred to as deleterious channelopathies, make individuals more susceptible to VT and VF.

On Epidemiology

In summary, ventricular arrhythmias like PVCs and VT can occur in healthy individuals but are more prevalent in older people and those with underlying heart disease. Nonsustained VT can be a sign of heart trouble and often prompts further evaluation. VT and VF are significant contributors to cardiovascular deaths, and the underlying heart disease varies with age. Some cases of sudden cardiac death may be linked to genetic mutations affecting ion channels in the heart.

This explains the different mechanisms and causes of ventricular arrhythmias, including ventricular tachycardia (VT) and ventricular fibrillation (VF). Here's an explanation:

 

**Classification of Ventricular Arrhythmias by Mechanism:**

Ventricular arrhythmias are classified into three main categories based on their underlying mechanisms: re-entrant, triggered, or automatic.

 

1. **Re-entrant Mechanism:** This type of arrhythmia occurs when there's an abnormal electrical circuit in the heart. Re-entry usually results from a combination of conduction block in one pathway and slow conduction in another, allowing the electrical signal to "loop" and continue circulating (re-entry). It's often seen in individuals with scarred heart tissue due to conditions like previous heart attacks, inflammation, or genetic factors.

 

2. **Triggered Mechanism:** Triggered arrhythmias result from abnormal electrical impulses that occur after the normal heartbeat. There are two types:

   - **Early Afterdepolarizations:** These are oscillatory electrical signals that happen during the late phase of the heart's action potential due to delayed repolarization.

   - **Delayed Afterdepolarizations:** These occur when there's an abnormal increase in intracellular calcium, leading to brief electrical signals after the heart's action potential ends.

 

3. **Automatic Mechanism:** This type arises from an accelerated pacemaker activity in the heart, where the heart's natural pacemaker cells start firing too rapidly.

 

**Underlying Causes of Ventricular Arrhythmias:**

The causes of ventricular arrhythmias can vary depending on the mechanism:

 

- **Re-entrant VT:** Often associated with heart conditions like heart attacks, inflammation, fibrofatty infiltration, genetic disorders (like hypertrophic cardiomyopathy), and scarring from previous surgeries.

 

- **Triggered VT:** Can occur in conditions like Brugada syndrome (abnormal conduction in the right ventricle) or idiopathic VT with a focal site of origin in specific heart areas.

 

- **Torsades de Pointes VT:** Results from early afterdepolarizations during prolonged heart action potential, often due to genetic long QT syndromes or medications that prolong QT intervals.

 

- **Bundle Branch Re-entry VT:** May occur in normal hearts as nonsustained beats but can become sustained in individuals with heart enlargement and slow conduction due to heart or conduction system diseases.

 

- **Accelerated Pacemaker Activity:** This can be triggered by various factors, including inflammation, excess digoxin levels, electrolyte imbalances, and more.

 

- **Bidirectional VT:** Caused by calcium overload in heart cells due to genetic mutations or digitalis toxicity.

 

- **Ventricular Fibrillation (VF):** VF is a chaotic, high-frequency electrical activity in the ventricles, often considered an end stage of severe electrophysiologic abnormalities. The exact mechanisms initiating VF are not fully understood, but it can be the result of various severe electrical disturbances.

 

In summary, ventricular arrhythmias can have different causes and mechanisms, and they may occur in individuals with various heart conditions or as a result of genetic factors, medication, or electrolyte imbalances. Ventricular fibrillation (VF) represents a particularly chaotic and life-threatening form of ventricular arrhythmia.

 

 

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Category: Medical sciences and health

• medicine
• cardiovascular
• chest

Here we explain how patients with suspected arrhythmias may show various symptoms and how these symptoms can help determine the severity, diagnosis, and treatment.

Patients with Suspected Arrhythmias May Show Different Symptoms:

 

•Common symptoms include palpitations (feeling irregular heartbeats), syncope (fainting), and feeling like they might faint (presyncope).

•Sometimes, arrhythmias can cause subtler signs like feeling tired, having less stamina, or vague discomfort, and occasionally, patients may have no symptoms at all.

•In rare cases, arrhythmias can lead to sudden cardiac arrest.

 

Severity and Underlying Heart Condition Matter:

 

•The seriousness of symptoms, especially if they cause fainting, and whether the patient has underlying heart problems determine the diagnosis and outlook.

•Patients with structural heart issues have a higher risk of life-threatening arrhythmias like ventricular tachycardia or ventricular fibrillation.

•Detecting whether there’s structural heart disease is crucial in diagnosing and predicting the outcome for those with suspected arrhythmias.

 

Exception for Family History:

 

•In cases where patients have a strong family history suggesting an inherited arrhythmia disorder (like long QT syndrome or Brugada syndrome), a family history of fainting or sudden death should prompt referral to a heart rhythm specialist, even if there’s no structural heart disease.

 

In summary, diagnosing and managing arrhythmias depends on the symptoms’ severity and the presence of underlying heart issues, but a family history of specific arrhythmia disorders can also be important.

Palpitations are feelings of irregular or fast heartbeats. They're often caused by abnormal beats called premature atrial contractions (PACs) and premature ventricular contractions (PVCs) or by rapid heart rhythms known as tachyarrhythmias. To figure out if palpitations need further evaluation, doctors consider the patient's description.

 

When patients have an irregular, unpredictable pattern of palpitations, it could be due to atrial fibrillation. A regular, fast pattern may suggest a sustained fast heart rate. Feeling a strong, regular pounding sensation in the neck may indicate palpitations from a fast heart rhythm.

 

In contrast, those who feel symptoms from PACs or PVCs are often more aware of the pause or the strong beat that follows the premature beat than the early beat itself. If these symptoms only occur occasionally and the patient has no other problems or heart disease, they usually don't need further checks.

 

However, if the symptoms happen more often, are severe, or come with near-fainting or fainting, they need further assessment. Antiarrhythmic medications are usually not needed for treating PACs or PVCs unless the symptoms are bothersome. β-Blockers, like metoprolol or atenolol, are often used to treat highly symptomatic patients with documented PACs or PVCs. Recent research suggests that patients with PVCs making up more than 24% of their heartbeats during 24-hour monitoring might have a higher risk of developing PVC-related heart problems.

 

Palpitations are most often linked to fast heart rhythms (tachyarrhythmias), while slow heart rhythms (bradyarrhythmias) rarely cause palpitations. Most fast heart rhythms in patients without heart disease are due to supraventricular tachycardias, which often resolve on their own within seconds. If a fast heart rhythm lasts longer, it can often be stopped with simple actions. Patients can cough, do the Valsalva maneuver, forcefully exhale with a closed throat, or gently rub their eyes to stop the rhythm. Doctors can also perform carotid sinus massage, but this should be avoided in elderly patients and those with certain medical conditions.

 

In patients with heart disease, palpitations might signal ventricular tachycardia, especially if accompanied by fainting or near-fainting. Occasionally, someone without heart disease might have idiopathic ventricular tachycardia, typically arising from specific heart areas. These cases often have a good outcome with ablation.

Syncope, which is a sudden loss of consciousness, and presyncope, a feeling of lightheadedness, happen when blood flow to the brain is temporarily reduced. This can be due to various reasons, including heart rhythm issues like tachyarrhythmias, bradyarrhythmias, or neurocardiogenic syncope. But sometimes, it can occur without any heart rhythm problems. To understand the cause, doctors need to carefully examine the patient's medical history and perform a physical examination to rule out other heart or neurological problems.

 

Certain aspects of the patient's history can point to heart rhythm issues as the cause. For instance, if syncope is linked to palpitations and there are no neurological issues before or after the episode, it might be due to a heart rhythm problem. Syncope can also be caused by conditions like aortic stenosis or left ventricular outflow obstruction.

 

Distinguishing between syncope and other conditions like vertigo, ataxia, or seizures is important. While syncope involves a loss of consciousness, vertigo feels like the room is spinning, ataxia results in a lack of balance, and seizures involve uncontrolled body movements. Postictal symptoms, which occur after seizures, are absent in syncope cases.

 

To diagnose the cause of syncope, it's crucial to gather detailed information about each episode, including what happened before, during, and after. Knowing the patient's activities, position, and symptoms when the episode started can provide valuable clues. For instance, if the loss of consciousness happens rapidly without warning, it could be due to seizures or certain arrhythmias. Palpitations during the warning signs may indicate a tachyarrhythmia.

 

Additionally, descriptions of what occurred during the loss of consciousness from witnesses can help. Muscle movements during the event can sometimes be similar to seizures, so understanding the nature of these movements is important. The duration of confusion and disorientation after regaining consciousness is another key factor. In neurocardiogenic syncope, orientation is regained within seconds, while seizures typically have a longer period of confusion and agitation after regaining consciousness.

In summary, syncope and presyncope are episodes of temporary loss of consciousness or lightheadedness, and they can be caused by various factors, including heart rhythm problems. Gathering detailed information about the events and symptoms, along with careful examination, is essential to determine the cause and appropriate treatment.

 

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Category: Medical sciences and health

• medicine
• renal
• urinary

The kidney has several important functions, including getting rid of waste, maintaining the balance of water and various substances in the body, and producing hormones like vitamin D, erythropoietin, and renin. One unique role of the kidney is to filter out nitrogenous waste. When we deal with kidney problems, we mainly focus on issues related to this filtration process rather than individual ion or molecule handling.

 

For instance, someone might have trouble excreting acid, but we'd assess it in the context of metabolic acidosis, which has various causes beyond the kidney. In contrast, acute and chronic kidney diseases specifically concern problems with the kidney's filtering function. When this filtration is impaired, other kidney functions like hormone production and maintaining electrolyte balance may also be affected.

 

Diseases affecting the kidney's tubules can impact glomerular filtration rates and lead to acute or chronic kidney problems. Sometimes, early kidney disease only shows as changes in the quality of filtration, like having too much protein in the urine (albuminuria), rather than changes in the quantity of filtration and increased waste concentration. Even when the glomerular filtration rate (GFR) is normal, certain kidney issues can cause problems like blood in the urine without high protein levels. 

 

In this chapter, we discuss how to approach patients with acute kidney problems, different types of kidney syndromes (nephrotic and nephritic), tubulointerstitial diseases, vascular issues in the kidney, papillary necrosis, and chronic kidney disease.

Pathobiology

 

The kidneys contain about 2 million filters called glomeruli, which typically filter around 180 liters of fluid each day. These filters are selective and prevent cells and large proteins (over 60 kD in size) from entering the filtered fluid. Smaller proteins are sometimes filtered and then reabsorbed in the kidney's tubules, keeping the urine protein concentration low. When there's a problem with the quantity or quality of this filtration, it indicates kidney disease.

 

In kidney diseases, the normal glomerular filtration rate (GFR) can decrease suddenly within hours to days in cases of acute kidney injury or gradually over months to years in chronic kidney disease. An abrupt drop in GFR is the main factor for diagnosing acute kidney injury, but unusual urine findings can help identify the cause of the injury. In chronic kidney disease, early stages might only show signs like protein in the urine (ranging from very small amounts to a lot) and abnormal urine findings, such as a few cells or even visible blood or pus. As chronic kidney disease progresses, GFR continues to decline, and in severe cases, dialysis or transplantation becomes necessary to manage uremia.

 

To assess how well the kidneys are working, one of the most accurate methods is to measure the Glomerular Filtration Rate (GFR) using specialized markers. However, these tests are costly and time-consuming, so they’re not used routinely. Instead, doctors commonly estimate GFR using methods like serum creatinine concentration, calculated creatinine clearance, and equations based on serum creatinine.

 

The kidneys play crucial roles in filtering waste products, regulating various substances in the body (like water, salts, and acids), and producing hormones like vitamin D, erythropoietin, and renin. Kidneys filter out waste products from the blood, which is essential for maintaining good health. When we talk about kidney diseases, we mostly focus on problems related to this filtering process rather than isolated issues with processing individual substances.

 

For instance, a patient might have a specific problem with their kidneys’ ability to handle acids. In such cases, doctors evaluate them for metabolic acidosis, which is a condition where the body has too much acid. Kidney disease is often categorized as acute kidney injury or chronic kidney disease, which both pertain to issues with the kidney’s filtration function. When filtration is impaired, other kidney functions, like hormone production and electrolyte balance, can also be affected.

 

Diseases affecting the kidney tubules, such as acute tubular necrosis and tubulointerstitial disease, can reduce the rate of glomerular filtration, leading to acute or chronic kidney problems. In some cases of early chronic kidney disease, the decrease in filtration quality (like the presence of albuminuria in urine) may be more noticeable than a reduction in the quantity of filtrate with increased nitrogenous waste. Sometimes, despite kidney filtration issues that cause significant proteinuria (excess protein in urine), the glomerular filtration rate (GFR) may still appear normal. Problems with the kidney’s filter can also allow certain cells like red blood cells (RBCs) to pass into the urine, which can be seen in conditions like the acute nephritic syndrome.

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In summary, kidney function is crucial for various bodily processes, and assessing it is essential for diagnosing and managing kidney diseases. Estimating GFR through serum creatinine levels is common, but it has limitations, as creatinine levels can be influenced by factors like muscle mass, age, and gender. An increase in serum creatinine over time can indicate kidney problems, and even a small rise can signify a significant decrease in GFR.

Approach to Diagnosis:

 

Doctors usually don’t recommend routine kidney screening for healthy adults without kidney disease risks. Kidney issues are often found when looking into other health problems. To assess kidney function, doctors follow a structured process.

 

They start with the serum creatinine level and GFR, which gives an estimate of kidney function. In some cases, they might confirm results using additional tests like cystatin C or a formal creatinine clearance test with a 24-hour urine collection. Creatinine clearance measures how fast your kidneys filter waste from your blood. It’s calculated using a formula:

 

Creatinine Clearance (CCr) = (Urine Creatinine × Urine Flow Rate) / Plasma Creatinine

 

This method tends to overestimate GFR by about 10% because creatinine isn’t just filtered; it’s also secreted into urine by kidney tubules. Collecting urine for 24 hours to calculate creatinine clearance can be tricky for patients and prone to errors.

 

Due to these challenges, doctors often rely on equations to estimate GFR based on simpler clinical data and lab results. The commonly used ones are the Cockcroft-Gault, the Modification of Diet in Renal Disease (MDRD) Study, and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations. The choice depends on the situation.

 

The Cockcroft-Gault equation can be problematic when estimating GFR for individuals with unusual body weight. The MDRD equations, while accessible, tend to underestimate GFR when creatinine levels are high, possibly leading to incorrect chronic kidney disease diagnoses. The CKD-EPI equation is considered more precise, especially for higher GFR values. Cystatin C may be useful for patients with upper-normal creatinine levels, but it doesn’t replace estimated GFR for most clinical needs.

 

Urinalysis is a valuable test but is sometimes ordered unnecessarily for healthy individuals. It checks the color and appearance of urine and involves using special dipsticks and microscopic analysis.

 

•Urine Color: Normally, urine is yellow due to certain pigments. Abnormal colors can indicate various conditions.

•Specific Gravity: This measures urine concentration and can be affected by substances like glucose or dye. A specific gravity of 1.010, called isosthenuria, is linked to chronic kidney disease.

•Urine pH: Typically, urine is slightly acidic (pH 5). It can become alkaline after meals or in vegetarian diets. High pH might signal infection or certain kidney issues.

•Glucose: Detected using dipsticks, it can indicate conditions like diabetes or kidney tubule problems.

•Protein: Dipsticks mainly detect albumin. Different levels correspond to different amounts of protein in urine. Microalbuminuria is an early sign of kidney issues.

•Hemoglobin: Dipsticks use the peroxidase activity of hemoglobin. It’s sensitive for detecting blood, even in small amounts. Persistent microscopic blood can be a risk factor for kidney disease or other issues.

•Leukocytes: Detected by leukocyte esterase, it suggests infections or inflammation.

•Urine Sediment: Examines various particles in urine.

•Hematuria: Red blood cells (RBCs) in urine can originate from various places. Dysmorphic RBCs indicate glomerular issues.

•Pyuria: White blood cells (WBCs) are common in urinary tract infections but can also signal other problems.

•Casts and Crystals: Casts are formed in kidney tubules and can indicate different conditions. Crystals can be normal or hint at underlying issues.

Remember, urinalysis is a helpful tool but needs proper interpretation by a healthcare professional for an accurate diagnosis.