The 9 Abdominal Regions (Quadrants) — Anatomy, Pathology, Pharmacology, Surgery & Medicine

Anatomical Basis of the Nine-Region Division

• Two horizontal planes: Subcostal plane (below costal margins, at lower border of costal cartilage of rib X / vertebra LIII) and Intertubercular plane (connecting iliac crest tubercles / vertebra LV)
• Two vertical (midclavicular) planes: Running from midpoint of clavicles to midpoint between ASIS and pubic symphysis

Region 1: Right Hypochondrium (Right Subcostal)

Anatomy

• Liver (right lobe — primary location), gallbladder, hepatic flexure of colon, right kidney (upper pole), right adrenal gland, part of duodenum

Pathology

• Hepatitis (viral, alcoholic, autoimmune) — tender hepatomegaly
• Cholecystitis (acute/chronic) — Murphy's sign positive
• Cholelithiasis — biliary colic
• Liver abscess, hepatocellular carcinoma
• Subphrenic abscess

Pharmacology (POM)

• Ursodeoxycholic acid — dissolution of cholesterol gallstones; also used in primary biliary cholangitis
• Antivirals (tenofovir, entecavir for HBV; sofosbuvir/ledipasvir for HCV)
• Analgesics: Antispasmodics (hyoscine butylbromide) for biliary colic
• Avoid hepatotoxic drugs (paracetamol overdose, statins, isoniazid) — monitor LFTs

Surgery

• Laparoscopic cholecystectomy — gold standard for symptomatic gallstones (4-port technique; camera at umbilicus, working ports at epigastrium and right upper quadrant)
• Open cholecystectomy (Kocher's incision — right subcostal) for complicated cases
• ERCP + sphincterotomy for choledocholithiasis
• Liver resection (hepatectomy) for HCC/metastases

Medicine

• Murphy's sign (right subcostal tenderness on inspiration) — pathognomonic of cholecystitis
• RUQ pain + jaundice + fever = Charcot's triad (cholangitis)
• Courvoisier's law: palpable gallbladder + jaundice = likely malignancy (not gallstones)
• US abdomen is first-line imaging; MRCP for bile duct evaluation

Region 2: Epigastric Region

Anatomy

• Stomach, duodenum (D1, D2), liver (left lobe), pancreas (head and body), lesser omentum, abdominal aorta, inferior vena cava, coeliac axis

Pathology

• Peptic ulcer disease (gastric/duodenal) — burning epigastric pain, worse/better with food
• Acute pancreatitis — severe epigastric pain radiating to back
• Gastritis, GORD
• Aortic aneurysm (AAA) — pulsatile epigastric mass
• Gastric cancer

Pharmacology (POM)

• PPIs (omeprazole, lansoprazole) — first-line for GORD, peptic ulcer, H. pylori eradication
• H2-blockers (ranitidine, famotidine) — second-line
• H. pylori triple therapy: PPI + clarithromycin + amoxicillin (7–14 days)
• Antacids (magnesium hydroxide, aluminium hydroxide) — symptomatic relief
• Octreotide — reduces pancreatic secretions in acute pancreatitis
• IV morphine or pethidine for severe pancreatitis pain
• Prokinetics (metoclopramide, domperidone) for gastroparesis/GORD

Surgery

• Truncal vagotomy + pyloroplasty (historical) for peptic ulcer
• Billroth I/II gastrectomy or Roux-en-Y reconstruction for gastric cancer
• Whipple's procedure (pancreaticoduodenectomy) for pancreatic head/periampullary cancer
• Endoscopic hemostasis for bleeding peptic ulcer (adrenaline injection, clips)
• AAA repair — open (midline laparotomy) or EVAR (endovascular)

Medicine

• Ranson's criteria / APACHE II / Glasgow score for pancreatitis severity
• Cullen's sign (periumbilical bruising) + Grey Turner's sign (flank bruising) = severe pancreatitis with retroperitoneal hemorrhage
• H. pylori testing: urea breath test, stool antigen, biopsy (CLO test)
• Epigastric pain + ECG changes → rule out inferior MI (referred pain via phrenic nerve)

Region 3: Left Hypochondrium (Left Subcostal)

Anatomy

• Spleen, tail of pancreas, stomach (fundus), left kidney (upper pole), left adrenal gland, splenic flexure of colon

Pathology

• Splenomegaly (malaria, CML, portal hypertension, EBV, lymphoma)
• Splenic injury/rupture — trauma; Kehr's sign (left shoulder tip pain)
• Splenic infarct — sickle cell disease, emboli
• Gastric volvulus
• Subphrenic abscess (left)

Pharmacology (POM)

• Hydroxycarbamide (hydroxyurea) — reduces sickling crises; prevents splenic infarction in sickle cell disease
• Anti-malarials (artemisinin-based, chloroquine, quinine)
• Penicillin V prophylaxis — lifelong post-splenectomy to prevent overwhelming post-splenectomy infection (OPSI)
• Vaccines post-splenectomy: pneumococcal (PCV13/PPSV23), meningococcal (ACWY + B), Hib, annual influenza

Surgery

• Splenectomy (laparoscopic preferred) — for trauma, ITP refractory to treatment, hereditary spherocytosis, hypersplenism
• Splenic artery embolization (non-operative management of splenic laceration grade I–III)
• Distal pancreatectomy ± splenectomy for pancreatic tail tumours

Medicine

• Massive splenomegaly causes: CML, myelofibrosis, visceral leishmaniasis (kala-azar), tropical splenomegaly
• Traube's space dullness on percussion indicates splenomegaly
• OPSI — potentially fatal; highest risk in first 2 years post-splenectomy; caused by encapsulated organisms (S. pneumoniae, N. meningitidis, H. influenzae)

Region 4: Right Flank (Right Lumbar / Right Lateral)

Anatomy

• Ascending colon, right kidney (main body), right ureter, small intestinal loops, right psoas muscle, right quadratus lumborum

Pathology

• Renal colic (ureteric stones) — severe colicky loin-to-groin pain, hematuria
• Pyelonephritis — loin pain, fever, dysuria; positive renal angle tenderness (CVAT)
• Renal cell carcinoma — classic triad: hematuria, loin pain, palpable mass
• Crohn's disease (right-sided involvement)
• Retroperitoneal fibrosis

Pharmacology (POM)

• Alpha-blockers (tamsulosin) — facilitate ureteric stone passage (medical expulsive therapy)
• NSAIDs (diclofenac IV/IM) — first-line analgesia for renal colic (reduces ureteral spasm + prostaglandin-mediated inflammation)
• Opioids (morphine, pethidine) — adjunct for severe renal colic
• Antibiotics for pyelonephritis: ciprofloxacin or co-amoxiclav (7–14 days); IV gentamicin + amoxicillin if severe
• Sunitinib, pazopanib, nivolumab — targeted/immunotherapy for metastatic RCC

Surgery

• Ureteroscopy + laser lithotripsy for ureteric calculi
• ESWL (extracorporeal shock wave lithotripsy) for renal/proximal ureteric stones
• Percutaneous nephrolithotomy (PCNL) for large staghorn calculi
• Radical nephrectomy for RCC
• Right hemicolectomy for Crohn's stricture / ascending colon cancer

Medicine

• Renal angle tenderness (costovertebral angle) — pyelonephritis vs. musculoskeletal vs. renal colic
• Urinalysis + urine culture mandatory; CT KUB (non-contrast) is gold standard for renal/ureteric calculi
• ACE inhibitors/ARBs for renoprotection in diabetic nephropathy

Region 5: Umbilical Region (Periumbilical)

Anatomy

• Small intestine (jejunum, ileum), transverse colon, abdominal aorta, inferior mesenteric artery origin, lymph nodes, umbilicus, mesentery

Pathology

• Small bowel obstruction — colicky periumbilical pain, distension, vomiting, absolute constipation
• Aortic aneurysm (AAA) — pulsatile mass at/above umbilicus; pain may radiate to back
• Mesenteric ischemia — "pain out of proportion to signs"; postprandial angina
• Umbilical hernia
• Early appendicitis — visceral pain starts periumbilical before migrating to RIF (McBurney's point)

Pharmacology (POM)

• IV fluids (crystalloids) + nasogastric decompression for bowel obstruction
• Anticoagulants (heparin, warfarin) — prevent/treat mesenteric venous thrombosis
• Thrombolytics / papaverine — intra-arterial for acute mesenteric ischemia (non-occlusive)
• Antifibrinolytics are avoided
• Beta-blockers — reduce AAA expansion rate (evidence for propranolol; currently used perioperatively)
• Statins — slow aneurysm growth and reduce cardiovascular events

Surgery

• Emergency laparotomy — for ruptured AAA (massive mortality); EVAR if available
• Elective AAA repair — when >5.5 cm (men), >5 cm (women), or rapid expansion
• Adhesiolysis — for adhesion-related SBO (laparoscopic or open)
• Bowel resection — for mesenteric ischemia with necrosis (second-look laparotomy at 24–48 h)
• Umbilical hernia repair — mesh or primary suture

Medicine

• Cullen's sign (periumbilical bruising) = hemorrhagic pancreatitis or ruptured ectopic pregnancy
• Sister Mary Joseph nodule = periumbilical lymph node metastasis from intra-abdominal malignancy
• Aortic bruit on auscultation → investigate with US abdomen for AAA
• Small bowel obstruction: "ladder pattern" (dilated loops with valvulae conniventes) on plain AXR

Region 6: Left Flank (Left Lumbar / Left Lateral)

Anatomy

• Descending colon, left kidney, left ureter, small bowel loops, left psoas muscle, left quadratus lumborum

Pathology

• Renal colic (left ureteric stones)
• Pyelonephritis (left)
• Polycystic kidney disease (bilateral flank masses)
• Descending colon cancer — iron deficiency anemia, change in bowel habit
• Retroperitoneal hematoma

Pharmacology (POM)

• Same as right flank (NSAIDs, alpha-blockers for stones; antibiotics for UTI/pyelonephritis)
• FOLFOX / FOLFIRI (fluorouracil + oxaliplatin or irinotecan) — chemotherapy for colon cancer
• Bevacizumab (anti-VEGF) — add-on for metastatic colorectal cancer
• Tolvaptan — vasopressin receptor antagonist for ADPKD (slows cyst growth)

Surgery

• Same urological procedures as right flank
• Left hemicolectomy for descending colon cancer
• Bilateral laparoscopic nephrectomy in ADPKD (prior to transplantation if massive enlargement)

Medicine

• PKD: bilateral flank masses + hypertension + hematuria; associated with berry aneurysms (screen MRA)
• Descending colon cancer often presents with obstruction (narrower lumen than right colon); less likely to cause anemia than right-sided cancers

Region 7: Right Iliac Fossa (Right Groin / Right Inguinal Region)

Anatomy

• Appendix (most common position: retrocaecal, 65%), caecum, terminal ileum, right ovary + right fallopian tube (females), right ureter (lower), psoas muscle, inguinal ligament, femoral/inguinal canal structures

Pathology

• Acute appendicitis — most common surgical emergency worldwide
• Ectopic pregnancy (right) — acute pain; positive bhCG; US shows no intrauterine pregnancy
• Ovarian cyst / Mittelschmerz / Ovarian torsion
• Mesenteric adenitis (children — mimics appendicitis)
• Inguinal hernia (indirect most common, especially in males)
• Crohn's disease (terminal ileitis)
• Caecal carcinoma
• Psoas abscess

Pharmacology (POM)

• IV antibiotics pre-/post-appendicectomy: cefuroxime + metronidazole (covers aerobes + anaerobes)
• Piperacillin-tazobactam or meropenem for complicated (perforated) appendicitis
• Analgesia: IV opioids (morphine) — does NOT mask peritonism in studies; safe to give
• Methotrexate — medical management of ectopic pregnancy (if unruptured, β-hCG <3000, no cardiac activity)
• Mesalazine / azathioprine / biologics (infliximab, adalimumab) — Crohn's disease management

Surgery

• Laparoscopic appendicectomy — standard of care; McBurney's point incision used in open (grid-iron incision)
• Antibiotic-only management of uncomplicated appendicitis (Appendicitis Acuta trial) — controversial but gaining acceptance
• Appendicectomy + right hemicolectomy for caecal carcinoma found incidentally
• Inguinal hernia repair: open (Lichtenstein mesh) or laparoscopic (TEP/TAPP)
• Salpingectomy / salpingostomy for ectopic pregnancy

Medicine

• McBurney's point: 1/3 of the way from ASIS to umbilicus
• Rovsing's sign (palpation LIF causes RIF pain), Psoas sign, Obturator sign
• Alvarado score (MANTRELS) for appendicitis diagnosis
• In women of childbearing age: always check β-hCG before attributing RIF pain to appendicitis

Region 8: Pubic/Hypogastric Region (Suprapubic)

Anatomy

• Urinary bladder, uterus (body and cervix), fallopian tubes (bilateral), rectum/sigmoid colon junction, prostate (males), ureters (terminal portions), seminal vesicles

Pathology

• Pelvic inflammatory disease (PID) — bilateral lower abdominal pain, vaginal discharge, cervical excitation
• Ovarian cysts (bilateral)
• Cystitis / UTI — suprapubic pain, dysuria, frequency
• Bladder cancer — painless hematuria
• Fibroids (uterine leiomyomas) — menorrhagia, pressure symptoms
• Pelvic peritonitis / Pouch of Douglas abscess (pelvic abscess)
• BPH / prostate cancer (males)

Pharmacology (POM)

• Antibiotics for PID: doxycycline + metronidazole ± ceftriaxone (covers C. trachomatis, N. gonorrhoeae, anaerobes)
• Antibiotics for UTI: trimethoprim, nitrofurantoin (uncomplicated); ciprofloxacin (complicated)
• Antispasmodics / anticholinergics (oxybutynin, solifenacin) for overactive bladder
• 5-alpha reductase inhibitors (finasteride) + alpha-blockers (tamsulosin) for BPH
• GnRH agonists (leuprolide) for fibroids (induces medical menopause preoperatively)
• NSAIDs / mefenamic acid for dysmenorrhea and fibroid-related pain
• Combined oral contraceptive — suppresses endometriosis, reduces PID recurrence

Surgery

• Laparoscopic drainage of pelvic abscess (Pouch of Douglas)
• TURP / laser prostatectomy for BPH
• Radical cystectomy + neobladder for muscle-invasive bladder cancer
• Total abdominal hysterectomy ± bilateral salpingo-oophorectomy (TAH-BSO) for fibroids/cancer
• Anterior/posterior repair (colporrhaphy) for pelvic organ prolapse
• Pelvic lymph node dissection — staging for cervical/endometrial/bladder malignancy

Medicine

• Fitz-Hugh-Curtis syndrome: right upper quadrant pain (perihepatic adhesions) secondary to ascending PID — mimics cholecystitis
• Cervical motion tenderness (chandelier sign) = PID
• PSA + TRUS-guided biopsy for prostate cancer; Gleason score for grading
• Bimanual examination essential for pelvic pathology; transvaginal US for ovarian/uterine lesions

Region 9: Left Iliac Fossa (Left Groin / Left Inguinal Region)

Anatomy

• Sigmoid colon, descending colon (lower), left ovary + left fallopian tube (females), left ureter (lower), inguinal structures (left), psoas muscle (left lower)

Pathology

• Diverticulitis — "left-sided appendicitis"; older patients; LIF pain, fever, altered bowel habit
• Diverticular abscess / perforation — peritonitis, pneumoperitoneum
• Sigmoid colon cancer — change in bowel habit, bleeding PR, obstruction
• Ectopic pregnancy (left)
• Ovarian pathology (left) — same as right
• Inguinal hernia (left)
• Constipation (very common cause of LIF pain, especially elderly)

Pharmacology (POM)

• Antibiotics for uncomplicated diverticulitis: metronidazole + ciprofloxacin (outpatient); IV co-amoxiclav or piperacillin-tazobactam (inpatient)
• Recent evidence (DIABOLO trial, AVOD trial): antibiotics may not be needed for uncomplicated acute diverticulitis — conservative management (bowel rest, analgesia) gaining acceptance
• Mesalazine — reduces recurrence of diverticulitis (limited evidence)
• High-fibre diet — prevents diverticular disease progression
• FOLFOX/FOLFIRI + bevacizumab — for metastatic sigmoid colon cancer
• Osmotic laxatives (lactulose, macrogol) and stimulant laxatives (senna, bisacodyl) for constipation

Surgery

• Hartmann's procedure — emergency sigmoid resection + end colostomy (for perforated diverticulitis with Hinchey III/IV peritonitis)
• Laparoscopic sigmoid colectomy — elective, after resolution of recurrent/complicated diverticulitis (usually ≥2 attacks or single complicated episode)
• Emergency Hartmann's reversal — reconnection of Hartmann's stoma (colostomy takedown)
• Anterior resection — for sigmoid colon / upper rectal cancer (with or without defunctioning ileostomy)
• Abdominoperineal resection (APR) — for low rectal cancer where sphincter cannot be preserved

Medicine

• Hinchey classification for perforated diverticulitis (I: pericolic abscess → IV: fecal peritonitis)
• CT abdomen/pelvis with IV contrast is the investigation of choice
• Colonoscopy contraindicated in acute diverticulitis (risk of perforation) — perform 6–8 weeks after resolution
• Diverticular disease vs. diverticulitis: former is asymptomatic; latter implies infection/inflammation

Summary Table

• Gray's Anatomy for Students, Nine-region pattern (block2, p. 336)
• Bailey and Love's Short Practice of Surgery, 28th Edition, Figure 63.2
• Tintinalli's Emergency Medicine, Rosen's Emergency Medicine, Sleisenger & Fordtran's Gastrointestinal and Liver Disease, Yamada's Textbook of Gastroenterology — clinical correlations throughout

• Cover page with both anatomical diagrams (Gray's Anatomy nine-region diagram + Bailey & Love clinical pain sites illustration)
• 9 region sections, each covering:
  • Anatomy (key organs)
  • Pathology (key diseases)
  • Pharmacology/POM (key drugs with mechanisms)
  • Surgery (key procedures)
  • Medicine (clinical signs, investigations, pearls)
• Full summary table of all 9 regions at the end
• References from Gray's Anatomy, Bailey & Love, Tintinalli's, Rosen's, Sabiston's, and more