Comprehensive Study Notes: Hepatic Physiology, Hepatitis, Irritable Bowel Syndrome, and Diverticular Disease

Hepatic Physiology and Diagnostic Testing

• Functions of the Liver:

  • Produces bile and cholesterol.

  • Converts excess glucose into glycogen for metabolic storage.

  • Filters and detoxifies the blood.

  • Regulates blood clotting mechanisms.

  • Produces bilirubin.

• Anatomy of the Liver:

  • Anatomically consists of $4$ lobes separated by the falciform ligament.

  • Weighs approximately $3\,\text{lbs}$.

• Liver Function Panel:

  • Total protein

  • Albumin

  • Bilirubin

  • Liver enzymes:

    • Alanine aminotransferase (ALT)

    • Aspartate aminotransferase (AST)

  • Alkaline phosphatase

Hepatitis Overview and Viral Variants

• Definition and General Etiology:

  • Inflammation of the liver, typically caused by exposure to an infectious agent, a toxin, or a medication/drug.

  • Viral Classifications: Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis D, Hepatitis E, and Hepatitis G.

  • Non-Viral Classifications: Autoimmune Hepatitis and Toxic Hepatitis.

• Hepatitis A (HAV):

  • Pathophysiology: Contagious acute infection caused by the Hepatitis A virus. Does not cause long-term effects or permanent liver damage, with most patients recovering in approximately $6\,\text{weeks}$.

  • Transmission Routes: Fecal-oral route, including drinking contaminated water, eating raw shellfish harvested from polluted water, diaper changing, oral-anal intercourse, sexual intercourse, or needle sharing.

  • Clinical Manifestations: May present with no symptoms, or with fatigue, nausea, vomiting, right upper quadrant (RUQ) abdominal pain, loss of appetite, low-grade fever, dark urine, muscle pain, and jaundice.

  • Testing and Diagnosis: Evaluated via blood tests measuring bilirubin and liver enzyme levels (ALT and AST). Diagnostic confirmation is performed using a radioimmunoassay special blood test: Anti-HAV IgM antibody test.

  • Treatment and Prevention: No specific antiviral treatment exists; primary focus is adequate nutrition, avoiding alcohol, and preventing liver damage. Prevention relies on proper handwashing and the Hepatitis A vaccine (included in the standard childhood vaccine schedule).

• Hepatitis B (HBV):

  • Pathophysiology: Can develop into a chronic infection leading to cirrhosis, liver failure, or liver cancer, though most adults achieve full recovery. Transmission can occur vertically from mother to baby or via asymptomatic individuals.

  • Transmission Routes: Contact with blood and other body fluids through direct relationships, sexual intercourse, needle sharing, or razor sharing. Transmission does not occur through casual contact, using a telephone, or sharing a toilet seat.

  • Clinical Manifestations: May present with no symptoms, or with loss of appetite, nausea, vomiting, fatigue, right upper quadrant (RUQ) abdominal pain, dark urine, jaundice, and joint pain.

  • Diagnostic Serology:

    • Hepatitis B surface antigen (HBsAg): A positive ($+\text{-test}$) result indicates the patient is currently infected and can infect others; a negative ($-\text{-test}$) result indicates the patient is not infected.

    • Antibody to Hepatitis B surface antigen (anti-HBs): A positive ($+\text{-test}$) result indicates antibodies are present from a recent resolved infection or vaccination, meaning the individual cannot infect others.

  • Treatment Protocol:

    • Acute HBV: Clear on its own with no specific medication required.

    • Recent Known Exposure: Administer Hepatitis B Immune Globulin (HBIg) alongside the Hepatitis B vaccine if exposure occurred within the last $24\,\text{hours}$.

    • Chronic HBV: Incurable; treatment aims to decrease liver damage and prevent hepatic carcinoma.

    • Interferon 2 injections given for $6\text{--}12\,\text{months}$ to boost the immune system.

    • Antiviral medications taken long-term or for life.

    • Liver transplantation indicated if severe liver damage occurs.

• Hepatitis C (HCV):

  • Pathophysiology: Represents the most serious viral hepatitis variant. Patients are frequently asymptomatic (especially in the acute phase), but chronic infection can lead to cirrhosis, impaired liver function, and liver failure.

  • Transmission Routes: Sharing needles (tattooing, intravenous drug use), contact with contaminated body fluids, and maternal-fetal transmission.

  • Vaccine Status: No vaccine currently exists due to antigen shifts in the virus.

  • Clinical Manifestations: Fatigue, lack of appetite, nausea, vomiting, yellowing of skin (jaundice), and muscle/joint pain.

  • Diagnostic Testing:

    • HCV antibody test: Detects proteins indicating past or present exposure.

    • HCV RNA/PCR test (viral load test): Ordered if the HCV antibody test is positive or following recent high-risk exposure.

  • Testing Screening Indications: Individuals born between $1945\text{--}1965$, illegal intravenous substance injectors, individuals who received a blood transfusion prior to $1992$, hemodialysis patients, individuals with known exposure, individuals with known HIV, patients displaying signs and symptoms of liver disease, and children born to mothers with Hepatitis C.

  • Treatment and Management: Maintain proper nutrition, ensure adequate rest, avoid alcohol, and monitor viral load before and after $8\text{--}12\,\text{weeks}$ of therapy.

  • Pharmacotherapy: Direct-acting antivirals (DAA) such as Mavyret and Epclusa taken for $8\text{--}12\,\text{weeks}$, achieving a cure rate of $95\%$.

Irritable Bowel Syndrome (IBS)

• Definition and Etiology:

  • A functional disorder defined by gut sensitivity and altered motility that can affect any segment of the gastrointestinal (GI) tract.

  • Characterized by abdominal pain, cramping, bloating, and alterations in bowel habits including diarrhea (IBS-D) or constipation (IBS-C).

  • Possible Pathophysiologic Causes: Altered GI motility (fluctuating acceleration and slowing), luminal irritation, and potential hormonal changes associated with underlying anxiety or depression.

• Triggers:

  • Specific foods that trigger abdominal bloating.

  • Psychological or physical stress.

  • Concurrent acute illnesses.

• Diagnostic Criteria and Approach:

  • Physical Examination: Absence of structural or physical abnormalities; diagnosed through a process of elimination.

  • Formal Diagnostic Criteria: Abdominal pain and discomfort lasting at least $12\,\text{weeks}$ (non-consecutive) plus at least $2$ of the following features:

    • Change in stool frequency or consistency.

    • Stool urgency or a sensation of incomplete evacuation.

    • Presence of mucus in the stool.

    • Bloating or abdominal distension.

  • Red Flag Symptoms Requiring Additional Diagnostic Testing:

    • New onset of symptoms after age $50$ (rule out colon cancer).

    • Unexplained weight loss.

    • High fever.

• Diagnostic Testing Modalities:

  • Laboratory work and imaging studies.

  • Flexible sigmoidoscopy (visualizes strictly the rectum and sigmoid colon).

  • Colonoscopy.

  • CT of the abdomen.

  • Stool studies to rule out parasitic infections.

• Management Strategies:

  • Lifestyle and Behavioral Interventions: Stress management, small frequent meals, elimination of dairy and caffeine, regular exercise, yoga, massage, deep breathing, acupuncture, hypnosis, herbal remedies, and counseling.

  • Dietary Supplements and OTC Medications: Dietary fiber supplementation, short-term anti-diarrheal use (Imodium), laxatives, and probiotics.

  • Pharmacologic Treatments:

    • Lubiprostone (Amitiza): GI motility enhancer indicated for IBS with constipation (IBS-C).

    • Alosetron Hydrochloride (Lotronex): GI motility modulator indicated for IBS with diarrhea (IBS-D).

    • Selective Serotonin Reuptake Inhibitors (SSRIs).

Diverticular Disease

• Definitions:

  • Diverticulosis: Formation of small, marble-sized pouches that protrude through the muscular wall of the colon.

  • Diverticulitis: Acute inflammation of the intestinal pouches (diverticula).

• Pathophysiology and Anatomical Distribution:

  • Diverticula develop in naturally weak anatomical areas of the bowel wall.

  • Usually multiple present and measure less than $10\,\text{mm}$.

  • Predominantly localized in the descending sigmoid colon (in Asian populations, predominantly found in the ascending colon).

  • Affects $50\%$ of the population over age 60$.\n* **Risk Factors:**\n * Age greater than 60$years ($>60).\n * Inadequate dietary fiber, leading to hard stool that accentuates diverticular pressure.\n * Lack of physical exercise.\n * Family history of diverticular disease.\n * Diabetes Mellitus (DM), smoking, and obesity.\n* **Clinical Presentation:**\n * Severe left lower quadrant (LLQ) abdominal pain, rated 6\text{--}10/10 in severity.\n * Pain is aggravated by eating and relieved following a bowel movement.\n * Fever, nausea, vomiting, abdominal bloating, constipation, and a palpable abdominal mass.\n* **Differential Diagnosis:**\n * Colon cancer.\n * Meckel's diverticulum: A congenital birth defect present in 2\% of the population representing a persistent yolk stalk, forming a sac in the lower ileum of the small intestine.\n * Gynecologic pathology: Ovarian cyst, ectopic pregnancy, pelvic inflammatory disease (PID), and endometriosis.\n * Urologic pathology: Urinary tract infection (UTI) and kidney stones.\n * Inflammatory Bowel Disease (IBD).\n* **Diagnostic Modalities:**\n * CT of the abdomen is the diagnostic test of choice.\n * Colonoscopy must be avoided during acute flares due to the risk of scope-induced bowel perforation.\n* **Treatment Protocols:**\n * Mild / Uncomplicated Cases (patients able to tolerate liquids): Managed on an outpatient basis with clear liquids and oral antibiotics for 7\text{--}10\,\text{days}. Symptoms typically improve in a few days.\n * Severe / Complicated Cases (patients unable to tolerate liquids or aged over 85$): Managed on an inpatient basis with complete bowel rest, IV antibiotics, and vital sign monitoring. Once symptoms improve in a few days, diet is advanced and the patient is discharged on oral antibiotics for$7\text{--}10\,\text{days}.\n * Surgical Resection: Surgical excision of inflamed bowel segments, required based on the severity and extent of inflammation.\n* **Prevention and Lifestyle Recommendations:**\n * High-fiber diet (20\text{--}30\,\text{g/day}).\n * Daily exercise (30\,\text{min/day}$$), including weight training.

  • Increased water intake.

  • Promptly responding to bowel urges to prevent stool hardening and wall perforation.