Intestinal and anorectal disorders

Gluten-related disorders

Gluten-related disorders: celiac disease, non-celiac gluten (wheat) sensitivity, and wheat allergy, conditions triggered by gluten in wheat, rye, and barley; celiac disease affects about 1% of people and requires a lifelong gluten-free diet.

Goldberg-Shprintzen megacolon syndrome

Goldberg-Shprintzen megacolon syndrome (GOSHS, megacolon-microcephaly syndrome), rare autosomal recessive disorder from KIFBP/KIAA1279 mutations, combining Hirschsprung disease, microcephaly, intellectual disability, and facial dysmorphism.

Haemorrhoids

Haemorrhoids (piles) are swollen, inflamed veins around the anus or lower rectum, external or internal. About 1 in 20 Americans are affected; treatment ranges from fiber and sitz baths to banding and hemorrhoidectomy.

Haemorrhoids in pregnancy

Haemorrhoids (piles) in pregnancy: swollen anal cushions causing pain, itching, and bleeding, affecting roughly 30-40% of pregnant women, mainly in the third trimester. Treated with fiber, fluids, sitz baths, and topical preparations; usually resolve postpartum.

Helicobacter-pylori associated duodenal ulcer

Helicobacter-pylori associated duodenal ulcer (ICD-11 DA63.1) is a duodenal ulcer caused by chronic H. pylori infection, which accounts for over 90% of duodenal ulcers; eradication therapy, now optimized bismuth quadruple therapy for 14 days, cures the ulcer and prevents recurrence.

Hematochezia

Hematochezia, or bright red blood per rectum, is passage of fresh red or maroon blood from the rectum, usually from lower GI bleeding (diverticula, angiodysplasia, neoplasms, colitis, hemorrhoids) but occasionally a brisk upper GI bleed with hemodynamic instability.

Hyperactive bowel sounds

Hyperactive bowel sounds (borborygmi) are abnormally loud, increased gurgling intestinal noises, ICD-11 ME03.0, caused by diarrhea, eating, IBD, GI bleeding, or early bowel obstruction, with limited auscultation reliability.

Hyperplasia of appendix

Hyperplasia of appendix (ICD-11 DB11.1) is benign, reactive proliferation of appendiceal lymphoid tissue that can obstruct the lumen, mimic appendicitis, and be mistaken histologically for LAMN.

Hyperplastic duodenal polyp

Hyperplastic duodenal polyp (過形成性十二指腸ポリープ), ICD-11 DA53.0: a rare benign non-neoplastic duodenal epithelial growth, serrated microvesicular histology, often linked to H. pylori and gastroduodenal disease, treated by endoscopic resection.

Hypertrophied anal papillae

Hypertrophied anal papillae, also called fibrous anal polyps (ICD-11 DB71.2), are benign fibroepithelial growths at the anal dentate line, linked to chronic anal fissure in over 90% of cases and often mistaken for hemorrhoids or polyps.

Idiopathic malabsorption due to bile acid synthesis defects

Idiopathic malabsorption due to bile acid synthesis defects, also called idiopathic or primary bile acid malabsorption (type 2 bile acid diarrhea, ORPHA:84065), is an intestinal disorder of unknown cause in which hepatic overproduction of bile acids, driven by defective FXR-FGF19 feedback, causes chronic watery diarrhea often misdiagnosed as IBS-D.

Ileus

Paralytic ileus, also called adynamic or functional ileus, is temporary non-mechanical paralysis of intestinal peristalsis, most often after abdominal surgery; other causes include opioids, hypokalemia, and peritonitis. Treated supportively with bowel rest, IV fluids, and nasogastric suction.

Incomplete defaecation

Incomplete defaecation, or sensation of incomplete evacuation, is the persistent feeling stool remains after a bowel movement; a Rome IV constipation criterion linked to dyssynergic defecation and obstructed defaecation syndrome.

Indeterminate colitis

Indeterminate colitis (IC), related to IBD unclassified (IBDU), is a provisional IBD diagnosis for colitis that cannot be classified as ulcerative colitis or Crohn's disease; IC is reserved for colectomy specimens, affects roughly 5-15% of colonic IBD, and mostly behaves like UC.

Infant dyschezia

Infant dyschezia (grunting baby syndrome), Rome IV G6 functional GI disorder: infants under 9 months strain and cry 10+ minutes before soft stools, from poor abdominal-pelvic floor coordination; self-limited, treated with reassurance only, distinct from constipation.

Infectious duodenitis

Infectious duodenitis, ICD-11 DA51.6, is duodenal mucosal inflammation caused by bacteria, viruses, fungi, or parasites; H. pylori is the most common cause, with giardiasis, tuberculosis, CMV, and MAI among others.

Inflammatory bowel disease

Inflammatory bowel disease (IBD): chronic relapsing-remitting gut inflammation, mainly Crohn's disease and ulcerative colitis. Distinguished by location (any GI tract vs colon only), rising global burden, and modern advanced-therapy guidelines.

Intestinal failure

Intestinal failure is the loss of gut absorptive function requiring intravenous support, classified as acute, prolonged acute, or chronic, and most often caused by short bowel syndrome.

Intestinal infectious diseases

Intestinal infectious diseases (gastroenteritis, infectious diarrhea, DOID:100): stomach and intestinal infections by viruses, bacteria, parasites, fungi; WHO ranks diarrheal disease third among child deaths, treated with oral rehydration solution and zinc.

Intestinal obstruction due to inspissated milk

Intestinal obstruction due to inspissated milk, also called inspissated milk syndrome or milk curd syndrome (ICD-11 KB87.0, ICD-10-CM P76.2), is a neonatal bowel obstruction from hard milk curds in premature infants fed high-energy formula, typically at the terminal ileum.

Intestinal obstruction of newborn

Neonatal intestinal obstruction (ICD-11 KB87, SNOMED 733145007): blockage of a newborn's GI tract from birth to 30 days, usually congenital, presenting with bilious vomiting, distention, and delayed meconium; classified as high or low obstruction.

Intra-abdominal hernia

Intra-abdominal hernia, also called internal or intraperitoneal hernia (ICD-11 DD50.2), is protrusion of viscera through peritoneal or mesenteric apertures; congenital paraduodenal and acquired post-bypass types cause closed-loop obstruction diagnosed by CT.

Intussusception (medical disorder)

Intussusception: telescoping of proximal bowel into distal bowel, the leading cause of intestinal obstruction in infants aged 3-36 months; diagnosed by ultrasound and treated by air or liquid enema reduction, with surgery for perforation, lead points, or failure.

Intussusception of appendix

Intussusception of the appendix (appendiceal intussusception), ICD-11 DB11.5, ICD-10 K38.8: rare telescoping of the vermiform appendix into itself or cecum, about 0.01% incidence, roughly 200 reported cases since McKidd's 1858 report.

Intussusception of small intestine

Intussusception of small intestine (ICD-11 DA91.0): telescoping of a proximal small bowel segment into a distal segment, causing obstruction and ischaemia; rare in adults, usually lead-point related, often treated surgically.

Intussusception of the large intestine

Intussusception of the large intestine: telescoping of bowel, usually ileum through the ileocecal valve into the colon. Common in infants, rare in adults, where malignancy is the usual lead point.

Irritable bowel syndrome

Irritable bowel syndrome (IBS), a disorder of gut-brain interaction, causes recurrent abdominal pain with altered bowel habits without structural damage; diagnosed by Rome IV criteria, treated with diet, drugs, CBT, and hypnotherapy.

Ischemic colitis

Ischaemic colitis, also called colon ischemia, is the most common gastrointestinal ischemia, caused by inadequate colonic blood flow, typically at watershed areas, presenting with abdominal pain and bloody diarrhea, managed supportively or surgically.

Ischiorectal abscess

Ischiorectal abscess (ischioanal abscess), second most common anorectal abscess, from anal gland infection spreading through the external sphincter into the ischiorectal fossa; treated by incision and drainage, often followed by fistula.