# Clinical Cases: GI Anatomy and Histology ## Case 1: Meckel's Diverticulum ### Patient Presentation **Demographics:** 18-month-old male **Chief Complaint:** Painless rectal bleeding **History of Present Illness:** Parents noticed brick-red blood mixed with stool during diaper changes for the past 2 days. The child has had three episodes of bloody stools without apparent abdominal pain, fever, or vomiting. He continues to feed normally and is playful between episodes. **Past Medical History:** Born at term, uncomplicated delivery, up-to-date on vaccinations ### Physical Examination - **Vital Signs:** Temperature 37.0C, HR 120 bpm, BP 85/55 mmHg, RR 24/min - **General:** Alert, active, well-hydrated infant - **Abdomen:** Soft, non-tender, non-distended, no palpable masses, normal bowel sounds - **Rectal:** External exam normal, hemoccult-positive stool ### Workup and Results - **CBC:** Hemoglobin 9.2 g/dL (decreased from baseline), MCV 78 fL - **BMP:** Within normal limits - **Meckel Scan (Technetium-99m pertechnetate scintigraphy):** Focal uptake in the right lower quadrant consistent with ectopic gastric mucosa ![Meckel Scan](case_01_image.jpg) *Technetium-99m pertechnetate scan showing focal uptake in the right lower quadrant (arrow), indicating ectopic gastric mucosa within a Meckel's diverticulum.* **Image Source:** Case courtesy of Radiopaedia.org ### Diagnosis **Meckel's Diverticulum with GI Bleeding** ### Clinical Correlation to Anatomy Meckel's diverticulum results from incomplete obliteration of the vitelline (omphalomesenteric) duct during embryonic development. It is a true diverticulum located on the antimesenteric border of the ileum, typically within 2 feet of the ileocecal valve. Approximately 50% contain ectopic tissue, most commonly gastric mucosa, which secretes acid causing ulceration of adjacent ileal mucosa and painless bleeding. ### Treatment - Surgical resection of the diverticulum with adjacent ileal segment - Laparoscopic approach preferred when feasible - Blood transfusion if hemodynamically significant --- ## Case 2: Barrett's Esophagus ### Patient Presentation **Demographics:** 58-year-old male **Chief Complaint:** Long-standing heartburn with recent difficulty swallowing **History of Present Illness:** The patient reports 15 years of heartburn and regurgitation, worse after meals and when lying down. He has used over-the-counter antacids intermittently with partial relief. Over the past 3 months, he has noticed solid foods "getting stuck" in his chest, requiring him to drink water to help them pass. **Past Medical History:** Obesity (BMI 34), hypertension, type 2 diabetes **Social History:** 20 pack-year smoking history (quit 5 years ago), occasional alcohol use ### Physical Examination - **Vital Signs:** BP 138/88 mmHg, HR 78 bpm, BMI 34 - **General:** Obese male in no acute distress - **Abdomen:** Soft, obese, non-tender, no masses - **Oropharynx:** Normal ### Workup and Results - **Upper Endoscopy:** Salmon-colored tongues of mucosa extending 4 cm above the gastroesophageal junction; biopsies obtained - **Histopathology:** Intestinal metaplasia with goblet cells; no dysplasia identified ![Barrett's Esophagus Endoscopy](case_02_image.jpg) *Endoscopic image of Barrett's esophagus showing characteristic salmon-colored columnar epithelium extending proximally from the gastroesophageal junction into the normally pale squamous esophagus.* **Image Source:** Wikimedia Commons, CC BY-SA 3.0 ### Diagnosis **Barrett's Esophagus without Dysplasia** ### Clinical Correlation to Histology The normal esophageal epithelium is stratified squamous non-keratinized, adapted for abrasion resistance. In Barrett's esophagus, chronic acid and bile reflux injury triggers metaplasia - the replacement of squamous epithelium with intestinal-type columnar epithelium containing goblet cells. This represents an adaptive response that provides better protection against acid but creates premalignant tissue with increased risk for adenocarcinoma. ### Treatment - High-dose PPI therapy (twice daily) - Lifestyle modifications: weight loss, head of bed elevation, avoiding meals before bedtime - Surveillance endoscopy every 3-5 years for non-dysplastic Barrett's - Referral for ablation if dysplasia develops --- ## Case 3: Hirschsprung Disease ### Patient Presentation **Demographics:** 3-day-old male neonate **Chief Complaint:** Failure to pass meconium, abdominal distension **History of Present Illness:** Full-term male born via uncomplicated vaginal delivery has not passed meconium in the first 48 hours of life. The nursing staff noted progressive abdominal distension. The infant is feeding poorly and has had one episode of bilious vomiting. **Birth History:** Term delivery, Apgar 8/9, birth weight 3.4 kg ### Physical Examination - **Vital Signs:** Temperature 37.2C, HR 150 bpm, RR 48/min - **General:** Irritable neonate with distended abdomen - **Abdomen:** Markedly distended, tympanitic, visible bowel loops, no peritoneal signs - **Rectal:** Tight anal sphincter; after examination, explosive release of stool and gas with temporary relief of distension ### Workup and Results - **Abdominal X-ray:** Dilated bowel loops with absence of air in the rectum - **Contrast Enema:** Transition zone in the rectosigmoid with dilated proximal colon - **Rectal Suction Biopsy:** Absence of ganglion cells in the submucosal and myenteric plexuses; hypertrophied nerve fibers present ![Hirschsprung Contrast Enema](case_03_image.jpg) *Contrast enema demonstrating the transition zone in Hirschsprung disease, with narrow aganglionic distal segment and dilated ganglionic proximal colon.* **Image Source:** Case courtesy of Radiopaedia.org ### Diagnosis **Hirschsprung Disease (Congenital Aganglionic Megacolon)** ### Clinical Correlation to Enteric Nervous System Hirschsprung disease results from failure of neural crest cell migration during embryonic development, producing an aganglionic segment of distal colon lacking both myenteric (Auerbach's) and submucosal (Meissner's) plexuses. Without enteric nervous system ganglia, the affected segment cannot relax, maintaining tonic contraction that creates functional obstruction. The normal proximal colon dilates (megacolon) as it attempts to overcome the obstruction. ### Treatment - Initial stabilization with rectal irrigations to decompress - Surgical resection of the aganglionic segment (pull-through procedure) - Long-term monitoring for enterocolitis and continence issues