I. Definition & Epidemiologic Context Splenomegaly is defined as a spleen that exceeds the 95th percentile for age- and sex-matched controls—typically: Splenomegaly is a sign, not a diagnosis, reflecting underlying pathology. Its prevalence varies by etiology: up to 50% in acute Epstein–Barr virus (EBV) mononucleosis, 30–40% in sickle cell disease (SCD), and <2% in asymptomatic…
Epidemiology and Pathophysiology Insulinomas are rare, typically benign (85–90%), functioning pancreatic neuroendocrine tumors (pNETs) arising from β-cells of the islets of Langerhans. Incidence is ~1–2 cases per million person-years, with a bimodal age distribution (peak incidence: 40–60 years), slight female predominance (F:M ≈ 2:3), and no racial predilection. Most are sporadic (95%); the remaining 5%…
Epidemiology and Burden of Disease Hepatitis A virus (HAV), a non-enveloped, positive-sense single-stranded RNA virus belonging to the Picornaviridae family (genus Orthohepatovirus), remains one of the most prevalent causes of acute viral hepatitis globally. According to WHO estimates, ~1.4 million symptomatic cases occur annually, though seroprevalence studies suggest that up to 80% of infections in…
Epidemiology and Global Burden Hepatitis E virus (HEV), a non-enveloped, positive-sense, single-stranded RNA virus belonging to the Hepeviridae family (genus Orthohepevirus, species HEV-A), is a globally significant cause of acute viral hepatitis. According to the WHO, HEV causes an estimated 20 million infections annually, resulting in 3.3 million symptomatic cases and over 44,000 deaths—primarily due…
Authored for clinicians with emphasis on evidence-based practice, updated guidelines (AASLD 2018, EASL 2017/2024 updates), and practical decision-making tools. Epidemiology & Virology Primer (Clinician Refresher) HBV is a Hepadnaviridae family, enveloped virus with a partially double-stranded, relaxed circular DNA genome. It replicates via an RNA intermediate using a viral reverse transcriptase — a feature conferring…
Authored with input from current guidelines: American Society of Colon and Rectal Surgeons (ASCRS) 2022, European Association of Endoscopic Surgery (EAES)/European Society of Gastrointestinal Endoscopy (ESGE) 2020, National Institute for Health and Care Excellence (NICE) NG143 (2019, reaffirmed 2022), and supported by key systematic reviews and meta-analyses (Cochrane Database Syst Rev 2023; PMID: 36758712; Lancet…
Definition and Pathophysiology Fecal impaction is a severe manifestation of chronic constipation characterized by the accumulation of hardened, dehydrated fecal matter in the rectum (rectal impaction) or proximal colon (colonic impaction) that cannot be evacuated spontaneously. Histopathologically, stool becomes hyperconcentrated due to prolonged colonic transit, resulting in excessive water and electrolyte absorption. This leads to…
Epidemiology & Clinical Relevance Anal fissures represent one of the most common causes of anorectal pain and hematochezia, affecting approximately 1 in 10 individuals at some point in life, with peak incidence in young to middle adulthood (20–40 years). Although both sexes are affected, posterior midline fissures predominate in women (due to childbirth-related trauma and…
Epidemiology and Clinical Significance Chronic functional constipation (CFC) affects approximately 12–27% of the general adult population, with prevalence rising sharply with age—up to 30–40% in individuals ≥65 years. It is more common in women (female-to-male ratio ~1.7:1), socioeconomic disadvantage, and sedentary lifestyle. Beyond reduced quality of life, constipation contributes significantly to healthcare utilization—accounting for over…
Epidemiology & Pathogenesis Giardia lamblia (syn. G. duodenalis, G. intestinalis) is a flagellated protozoan parasite and a leading cause of protozoal gastroenteritis worldwide. The CDC estimates over 280 million cases annually globally, with high prevalence in children <5 years in low-resource settings and outbreaks linked to waterborne or person-to-person transmission in high-income countries (WHO, 2023;…
Definition and Pathophysiology Lactose intolerance (LI) is a clinical syndrome characterized by the development of digestive symptoms following ingestion of lactose—the primary carbohydrate in mammalian milk. It results from lactose malabsorption (LM), defined as inadequate hydrolysis of lactose into glucose and galactose due to deficient or absent activity of brush-border enzyme lactase-phlorizin hydrolase (LCT) in…
Definition and Disease Spectrum Microscopic colitis (MC) is a chronic, immune-mediated inflammatory disorder of the colon characterized by persistent, non-bloody, watery diarrhea, with normal-appearing mucosa on endoscopy but distinctive histopathological features confined to the lamina propria. Two subtypes exist: Both subtypes share overlapping clinical features, risk factors, and treatment responses, suggesting a common pathophysiologic pathway—though…
Epidemiology & Clinical Spectrum Irritable bowel syndrome (IBS) affects ~10–15% of the global population, with a 2:1 female-to-male predominance. It is classified into subtypes based on stool morphology (Bristol Stool Scale): Pathophysiological underpinnings include: Precipitating factors: Diagnostic Evaluation: A Precision Medicine Approach 1. Rome IV Criteria (Required for Diagnosis) IBS is diagnosed when recurrent abdominal…
Definition & Epidemiology Acute heart failure (AHF) refers to the rapid onset or acute worsening of symptoms and/or signs of heart failure (HF), typically prompting urgent medical evaluation, emergency department (ED) visit, or hospitalization. It encompasses: Incidence: ~1–2 million hospitalizations/year in the U.S. Mortality remains high—30-day mortality ~10%, 1-year mortality ~25–30%—underscoring the need for rapid,…
I. Definition and Classification of Severely Elevated Blood Pressure Severely elevated blood pressure (SEBP) remains a common presenting condition in emergency departments and outpatient clinics. It is critical to distinguish between hypertensive emergency (a medical urgency requiring rapid, controlled BP reduction), asymptomatic markedly elevated BP (formerly “hypertensive urgency”), and asymptomatic elevated BP. Classification should be…
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