LE1 SUMMARY 2

Visceral pain — dull, poorly localized pain originating from stretching, distention, or ischemia of hollow organs, transmitted via slow C-fibers

What is the definition and mechanism of visceral pain?

Somatic pain — sharp, intense, precisely localized pain caused by direct irritation or inflammation of parietal peritoneum, transmitted via fast A-delta fibers

What is the definition and mechanism of somatic pain?

Referred pain — pain perceived in a cutaneous dermatome distant from the site of organ pathology due to shared spinal cord sensory convergence pathways

What is referred pain?

Epigastric region — upper abdominal area where visceral pain from embryologic foregut structures including stomach, duodenum, liver, gallbladder, and pancreas is perceived

Where is visceral pain from foregut organs localized?

Periumbilical region — mid-abdominal area where visceral pain from embryologic midgut structures including small bowel, appendix, cecum, and ascending colon is perceived

Where is visceral pain from midgut organs localized?

Hypogastrium or suprapubic region — lower abdominal area where visceral pain from embryologic hindgut structures including distal colon, rectum, and pelvic organs is perceived

Where is visceral pain from hindgut organs localized?

Impaired linear growth / stunting — unique pediatric red flag indicating irreversible consequences of undiagnosed chronic organic GI pathology

What is a unique pediatric red flag for organic GI disease on a growth chart?

Pediatric organic abdominal pain red flags — impaired linear growth, involuntary weight loss, bilious vomiting, nocturnal pain awakening child, persistent RLQ pain, GI blood loss, and fever above 39.4 C

What clinical red flags distinguish pediatric organic abdominal pain from functional disorders?

Biopsychosocial model — conceptual framework evaluating biological, psychological, and social factors interacting bidirectionally through the gut-brain axis in Disorders of Gut-Brain Interaction

Which conceptual framework guides the evaluation and management of Disorders of Gut-Brain Interaction?

Rome IV criteria — diagnostic framework using standardized symptom patterns, frequency, and duration to establish a positive diagnosis of DGBI without extensive testing

Which criteria are used to establish a positive diagnosis of Disorders of Gut-Brain Interaction?

Malingering vs DGBI — malingering involves conscious fabrication of pain for secondary gain, whereas DGBI involves genuine pain from altered gut-brain axis processing

How does malingering differ from a Disorder of Gut-Brain Interaction?

Carnett sign — physical exam maneuver where abdominal palpation is repeated while patient flexes rectus muscles; increased or unchanged pain indicates abdominal wall origin, while decreased pain indicates intra-abdominal origin

Which physical exam maneuver distinguishes abdominal wall pain from intra-abdominal pathology?

Rebound tenderness — severe pain elicited by sudden release of deep hand pressure during abdominal palpation, indicating parietal peritoneal inflammation

What physical exam finding indicates parietal peritoneal inflammation upon sudden release of pressure?

Costovertebral angle tenderness — pain elicited by fist percussion over the lower posterior rib cage at the 12th rib, indicating acute pyelonephritis or renal inflammation

Which physical exam maneuver assesses for acute pyelonephritis?

Dynamic (mechanical) obstruction — physical luminal blockage where intestinal peristalsis initially increases to work against a barrier before eventually failing

What defines dynamic mechanical intestinal obstruction?

Adynamic (functional) ileus — paralysis of intestinal peristalsis without physical luminal blockage, presenting with absent or hypoactive bowel sounds

What defines adynamic functional ileus?

Post-operative adhesions — single most common cause of small bowel obstruction in adults, accounting for approximately 60% of cases

What is the most common cause of small bowel obstruction in adults?

Colorectal adenocarcinoma — single most common cause of large bowel obstruction in adults

What is the leading cause of large bowel obstruction in adults?

Intestinal strangulation — surgical emergency occurring when compromised blood supply leads to intestinal ischemia, bowel wall necrosis, gangrene, and septic shock

What is intestinal strangulation?

High (proximal) small bowel obstruction — characterized by early, frequent, profuse bilious vomiting, minimal abdominal distention, and rapid fluid/electrolyte depletion

What are the clinical characteristics of high small bowel obstruction?

Low (distal) small bowel or colonic obstruction — characterized by marked abdominal distention, early obstipation, and late feculent vomiting

What are the clinical characteristics of low intestinal obstruction?

Closed-loop obstruction — dangerous obstruction type where a segment of bowel is blocked at both proximal and distal ends, leading to rapid arterial compromise and perforation

What defines a closed-loop bowel obstruction?

Acute Colonic Pseudo-Obstruction (Ogilvie Syndrome) — massive functional dilation of cecum and colon without mechanical obstruction, linked to autonomic dysfunction and CABG surgery

What is Ogilvie Syndrome, its associated surgical risk factor, and its pathophysiology?

Neostigmine — acetylcholinesterase inhibitor drug administered for pharmacological decompression in acute colonic pseudo-obstruction

Which medication is indicated for pharmacological decompression in Ogilvie Syndrome?

Interstitial cells of Cajal — pacemaking cells of the gut wall whose reduced density is implicated in chronic intestinal pseudo-obstruction

Which cells are reduced in density in chronic colonic pseudo-obstruction?

Intraluminal dynamic SBO causes — bezoars, impacted fecalomas, swallowed foreign bodies, gallstones, and heavy Ascaris lumbricoides infestation

What are primary intraluminal causes of mechanical small bowel obstruction?

Internal hernia common sites — foramen of Winslow, congenital mesenteric defects, defects in the broad ligament, and intersigmoid fossa

Where do internal hernias commonly entrap bowel loops?

Esophageal Squamous Cell Carcinoma vs Adenocarcinoma — squamous cell carcinoma arises in middle/upper third (linked to alcohol, smoking, African-American race), whereas adenocarcinoma arises in distal third (linked to GERD, Barrett esophagus, obesity, White race)

How do risk factors and locations differ between esophageal squamous cell carcinoma and adenocarcinoma?

Peptic ulcer disease — most common benign etiology causing gastric outlet obstruction via chronic scarring and edema

What is a common benign cause of gastric outlet obstruction?

Stepladder air-fluid levels — classic upright plain abdominal radiograph finding demonstrating multiple differential fluid levels in mechanical small bowel obstruction

Which plain radiograph finding on an upright film confirms mechanical SBO?

Physiologic midgut herniation — normal embryonic process occurring between 4 and 10 weeks of gestation where midgut rotates and herniates into umbilical cord before returning to abdominal cavity by week 10

What is physiologic midgut herniation and its gestational timeframe?

Gastroschisis — full-thickness abdominal wall defect located strictly to the RIGHT of an intact umbilicus, with viscera directly exposed to amniotic fluid without a membrane sac

What is gastroschisis and its anatomical location relative to the umbilicus?

Right omphalomesenteric artery interruption — vascular disruption theory explaining the pathogenesis of gastroschisis

Which vascular insult theory explains the etiology of gastroschisis?

Omphalocele — midline abdominal wall defect at the base of the umbilicus covered by a 3-layer protective sac of amnion, peritoneum, and Wharton jelly, frequently containing the liver

What is an omphalocele and its characteristic protective covering?

Amniotic fluid peritonitis — chemical inflammatory response causing thickening, matting, edema, and fibrous peel formation on exposed bowel loops in gastroschisis

Why are exposed bowel loops thickened and edematous in gastroschisis?

Associated congenital anomalies — present in greater than 50% of omphalocele cases (cardiac defects, neural tube defects, Beckwith-Wiedemann syndrome), but uncommon in gastroschisis (less than 10%)

How do coexisting congenital anomalies differ between omphalocele and gastroschisis?

Complex gastroschisis — gastroschisis complicated by intestinal atresia, stenosis, volvulus, or necrosis, serving as the primary determinant of infant morbidity and mortality

What defines complex gastroschisis and its prognostic significance?

Vanishing gastroschisis — severe intra-uterine complication where closure of the abdominal wall defect strangles herniated bowel, leading to total intestinal resorption or severe atresia

What is vanishing gastroschisis?

Hernia of the umbilical cord — cord base defect under 3 cm with intact sac containing small bowel loops, carrying a risk of bowel ligation during cord clamping

What is a hernia of the umbilical cord and its key procedural risk?

Spring-loaded silo reduction — staged surgical technique where exposed bowel is placed in a protective silicone silo and reduced daily into the abdominal cavity prior to delayed fascial closure

What is staged silo reduction in gastroschisis management?

Topical escharification — non-operative application of topical drying agents like silver sulfadiazine to promote eschar formation and epithelialization over a giant omphalocele sac when closure is unsafe

What is topical escharification in giant omphalocele management?

Beckwith-Wiedemann syndrome — congenital disorder characterized by omphalocele, macroglossia, gigantism, and neonatal hypoglycemia

Which congenital syndrome features omphalocele, macroglossia, and neonatal hypoglycemia?

Pentalogy of Cantrell — rare cephalic fold defect comprising supraumbilical omphalocele, lower sternal cleft, anterior diaphragmatic hernia, pericardial defect/ectopia cordis, and intracardiac anomaly

What five anomalies comprise the Pentalogy of Cantrell?

OEIS complex (Cloacal Exstrophy) — severe caudal fold defect characterized by Omphalocele, Exstrophy of bladder/hindgut, Imperforate anus, and Spinal defects

What does the OEIS complex stand for in cloacal exstrophy?

Mermaid cast — postoperative orthopedic cast applied after pelvic bone approximation in cloacal exstrophy reconstruction to prevent recurrent pubic diastasis

What is the purpose of a mermaid cast post-cloacal exstrophy repair?

Pediatric umbilical hernia — fascial ring defect at the umbilicus covered by intact skin, closing spontaneously in 90% of children by age 2; surgery indicated if defect greater than 1.5 cm persists past age 5

What is the natural history and surgical indication threshold for pediatric umbilical hernia?

Virchow node — left supraclavicular lymphadenopathy indicating metastatic intra-abdominal or gastrointestinal malignancy

What sign describes left supraclavicular lymph node enlargement in abdominal cancer?

Sister Mary Joseph nodule — metastatic periumbilical lymph node infiltration indicative of intra-abdominal or pelvic malignancy

What term describes a metastatic periumbilical mass?

Blumer shelf — palpable tumor nodule or firmness in the pelvic cul-de-sac on rectal or pelvic exam, indicating metastatic drop metastasis from gastric or GI cancer

What physical exam sign describes pelvic drop metastasis in GI cancer?

Krukenberg tumor — metastatic adenocarcinoma to the ovaries, classic for stomach or GI primary malignancies

What is a Krukenberg tumor?

CA 19-9 — serum tumor marker elevated in pancreatic ductal adenocarcinoma and biliary tract cancers

Which tumor marker is associated with pancreatic carcinoma?

Alpha-fetoprotein (AFP) — serum tumor marker characteristically elevated in Hepatocellular Carcinoma (HCC) and Hepatoblastoma

Which tumor marker is elevated in primary liver malignancies?

Carcinoembryonic Antigen (CEA) — serum tumor marker used for monitoring Colorectal Cancer recurrence

Which tumor marker is monitored in colorectal carcinoma?

CA 125 — serum tumor marker evaluated in suspected ovarian carcinoma presenting as a pelvic or abdominal mass

Which tumor marker evaluates suspected ovarian masses?

Prostate-Specific Antigen (PSA) — tumor marker evaluated when prostatic hypertrophy or carcinoma causes lower abdominal or urinary retention mass

Which marker evaluates lower abdominal mass from prostate pathology?

Vanilmandelic acid (VMA) and Homovanillic acid (HVA) — elevated urinary catecholamine metabolites measured to diagnose pediatric neuroblastoma

Which urinary catecholamines diagnose pediatric neuroblastoma?

Triphasic CT scan — dynamic contrast imaging protocol using arterial, portal venous, and delayed phases to evaluate liver mass vascularity

Which imaging protocol is optimal for characterizing hepatic lesions?

Gastrectomy with D2 lymph node dissection — gold standard definitive surgical resection for resectable gastric adenocarcinoma

What is the surgical treatment of choice for stomach cancer?

Gastrointestinal Stromal Tumor (GIST) — common mesenchymal tumor of GI tract originating from interstitial cells of Cajal, characterized by c-KIT (CD117) mutation

What is GIST, its cell of origin, and its diagnostic marker?

Imatinib — tyrosine kinase inhibitor drug used as targeted therapy for Gastrointestinal Stromal Tumors

Which targeted medication treats GIST?

Hepatic hemangioma — most common benign primary liver mass, showing centripetal peripheral-to-central enhancement on dynamic contrast CT

What is the most common benign liver tumor and its CT finding?

Hepatic adenoma — benign solid liver tumor strongly associated with long-term oral contraceptive use in premenopausal women, carrying risks of rupture and malignant transformation

Which liver tumor is linked to OCP use, and what are its risks?

Focal Nodular Hyperplasia (FNH) — benign hyperplastic liver lesion featuring a pathognomonic central stellate scar on contrast CT scan

Which liver lesion exhibits a central stellate scar?

Hepatocellular Carcinoma (HCC) — primary liver malignancy showing hypervascular arterial enhancement with portal venous washout on triphasic CT

What is the classic dynamic contrast CT pattern defining HCC?

Milan Criteria — single liver tumor less than 5 cm OR up to 3 tumors each less than 3 cm without vascular invasion, defining eligibility for curative liver transplantation

What are the Milan Criteria for liver transplantation in HCC?

Courvoisier sign — palpable, non-tender, enlarged gallbladder in a jaundiced patient, classic for malignant obstruction of distal bile duct by pancreatic head carcinoma

What is Courvoisier sign and its clinical significance?

Pancreaticoduodenectomy (Whipple procedure) — radical surgical resection of distal stomach, duodenum, head of pancreas, gallbladder, and distal bile duct for pancreatic head cancer

What is the Whipple procedure and which organs are resected?

Overwhelming Post-Splenectomy Infection (OPSI) — fulminant sepsis post-splenectomy caused by encapsulated bacteria (S. pneumoniae, H. influenzae, N. meningitidis), prevented by pre-op vaccination 2 weeks prior

What is OPSI, its causative organisms, and its preventive strategy?

Extended right hemicolectomy — indicated surgical resection for carcinomas located at the hepatic flexure or proximal transverse colon

Which surgical procedure is indicated for hepatic flexure colon cancer?

Age 45 — recommended age to initiate routine screening for Colorectal Cancer in average-risk adults

At what age should average-risk CRC screening begin?

Colonoscopy every 10 years — gold standard diagnostic and screening modality for Colorectal Cancer

What is the gold standard screening test and interval for CRC?

Right-sided colon cancer — presents with occult GI blood loss, iron deficiency anemia, RLQ mass, and fatigue, rarely obstructing early due to large lumen

How does right-sided colon cancer characteristically present?

Left-sided colon cancer — presents with change in bowel habits, hematochezia, crampy LLQ pain, and intestinal obstruction

How does left-sided colon cancer characteristically present?

Total Mesorectal Excision (TME) — surgical technique resecting rectal cancer en-bloc with intact mesorectal fat and lymph nodes to minimize local recurrence

What surgical technique minimizes local rectal cancer recurrence?

Low Anterior Resection (LAR) — sphincter-preserving surgical resection for cancers located in middle or upper rectum

Which surgical procedure resects middle/upper rectal cancer while preserving sphincters?

Abdominoperineal Resection (APR) — radical surgical resection of lower rectum, anal canal, and sphincter complex with permanent end colostomy

Which procedure is performed for low rectal cancers invading sphincters?

Ruptured Abdominal Aortic Aneurysm triad — severe abdominal or back pain, hypotension, and a pulsatile abdominal mass, occurring in full-thickness aortic dilation >=3 cm

What clinical triad indicates a ruptured AAA, and what size threshold defines AAA?

Retroperitoneal sarcoma — most common primary malignant tumor of retroperitoneum, predominantly Liposarcoma (50%) and Leiomyosarcoma (25%)

What is the most common primary retroperitoneal malignancy?

Neuroblastoma — most common primary malignant intra-abdominal tumor in pediatric patients, arising from neural crest cells

What is the most common pediatric intra-abdominal malignancy?

Hepatoblastoma — most common primary malignant liver tumor in children, associated with markedly elevated Alpha-fetoprotein

What is the most common primary pediatric liver cancer?

Diarrhea clinical definition — passage of abnormally liquid or unformed stools at an increased frequency, generally with a daily stool weight exceeding 200 g/day

What is the clinical definition and stool weight threshold for diarrhea?

Acute diarrhea — passage of abnormally liquid or unformed stools lasting less than 14 days (less than 2 weeks)

What is the duration threshold for acute diarrhea?

Persistent diarrhea — diarrhea lasting between 14 and 28 days (2 to 4 weeks)

What is the duration threshold for persistent diarrhea?

Chronic diarrhea — diarrhea lasting longer than 28 days (greater than 4 weeks)

What is the duration threshold for chronic diarrhea?

Pediatric chronic diarrhea definition — daily stool volume exceeding 10 g/kg/day in infants/toddlers or 200 g/day in older children, lasting 4 weeks or longer

What stool volume and duration define chronic diarrhea in pediatric patients?

Resuscitation and fluid stabilization — first priority in managing severe acute diarrhea before seeking etiologic pathogen diagnosis

What is the immediate clinical priority in severe acute diarrhea?

Osmotic diarrhea — mechanism caused by unabsorbed luminal solutes holding water in gut lumen, characteristically STOPPING OR IMPROVING WITH FASTING, with stool osmotic gap >50 to 100 mOsm/kg

What defines osmotic diarrhea, its response to fasting, and its stool osmotic gap?

Secretory diarrhea — mechanism caused by active mucosal electrolyte/fluid secretion, PERSISTING DESPITE FASTING, with stool osmotic gap <50 mOsm/kg

What defines secretory diarrhea, its response to fasting, and its stool osmotic gap?

Formula: 290 - 2 * (Stool Na + Stool K) — mathematical equation used to calculate the stool osmotic gap

How is the stool osmotic gap calculated?

Incubation 1 to 6 hours — rapid onset incubation period characteristic of preformed bacterial enterotoxins (Staphylococcus aureus, Bacillus cereus) causing profuse emesis

What is the incubation period for preformed bacterial toxins?

Reheated fried rice — food vehicle classically associated with Bacillus cereus preformed toxin food poisoning

Which food is classic for Bacillus cereus preformed toxin poisoning?

Vibrio cholerae — cause of severe enterotoxigenic rice water diarrhea via adenylate cyclase activation and cAMP hypersecretion

Which pathogen causes rice water stool and what is its cellular mechanism?

Shiga toxin-producing E. coli (STEC / EHEC) — pathogen causing bloody diarrhea after undercooked beef; ANTIMICROBIALS ARE STRICTLY CONTRAINDICATED DUE TO INCREASED RISK OF HEMOLYTIC UREMIC SYNDROME

Which pathogen causes bloody diarrhea after undercooked beef, and why are antibiotics contraindicated?

Hemolytic Uremic Syndrome (HUS) triad — microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury

What triad defines Hemolytic Uremic Syndrome?

Clostridioides difficile colitis — nosocomial inflammatory diarrhea following broad-spectrum antibiotics; diagnosed by clinical diarrhea plus toxigenic C. diff proof; treated with oral Vancomycin or Fidaxomicin

What is C. diff colitis, its diagnostic criteria, and its first-line treatment?

Glucose-facilitated sodium cotransport — intact enterocyte brush border transport mechanism providing the scientific basis for Oral Rehydration Therapy

Which transport mechanism enables Oral Rehydration Therapy?

Loperamide contraindications — febrile dysentery, bloody diarrhea, or invasive bacterial colitis, due to risk of toxic megacolon and increased toxin absorption

When is loperamide strictly contraindicated?

IMCI Plan A (No dehydration) — home fluid management, extra fluids, ORS after each stool, plus oral Zinc (10 to 20 mg/day for 10 to 14 days)

What is IMCI Plan A for pediatric diarrhea?

IMCI Plan B (Some dehydration) — administration of 75 mL/kg low-osmolarity WHO ORS orally over 3 to 4 hours in clinic

What is IMCI Plan B for pediatric diarrhea?

IMCI Plan C (Severe dehydration) — emergency IV fluid resuscitation with Ringer's Lactate (100 mL/kg split into 30 mL/kg bolus then 70 mL/kg maintenance over 3-6 hours)

What is IMCI Plan C for pediatric diarrhea?