Lower gastrointestinal congenital malformations Notes
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NOTES NOTES LOWER GASTROINTESTINAL CONGENITAL MALFORMATIONS GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Lower gastrointestinal tract structural/ functional anomalies during embryonic development; present at birth ▪ Malformations from duodenum to anus DIAGNOSIS DIAGNOSTIC IMAGING ▪ Prenatal ultrasound, MRI, CT scan/ radiography ▪ Avoid X-ray due to teratogenicity CAUSES TREATMENT ▪ Genetic, environmental factors SIGNS & SYMPTOMS SURGERY ▪ See individual disorders ▪ At birth: may be asymptomatic ▪ Malformations: relatively benign (nausea, vomiting, difﬁculty passing stool) to life incompatibility GASTROSCHISIS osms.it/gastroschisis PATHOLOGY & CAUSES ▪ Extrasomatic protrusion of intestines through hole in abdominal wall near umbilicus ▪ Hernia: affected organs exit cavity ▪ Week 4 of gestation: lateral folds fail to fuse → hole in abdominal wall → organs protrude ▪ Most common on right side ▪ Usually small intestine ▪ Stomach, liver may also protrude (rare) 316 OSMOSIS.ORG CAUSES ▪ Genetic, environmental factors RISK FACTORS ▪ Mother’s young age ▪ Exposure to teratogenic substances (alcohol, tobacco) COMPLICATIONS ▪ Intestinal inﬂammation due to intrauterine exposure to amniotic ﬂuid, malabsorption, infarction of intestinal tube due to compressed blood vessels, infection
Chapter 37 Lower Gastrointestinal Congenital Malformations SIGNS & SYMPTOMS ▪ During fetal life: asymptomatic ▪ At birth: difﬁculty feeding/passing stool DIAGNOSIS DIAGNOSTIC IMAGING Intrauterine ultrasound, MRI X-ray, CT scan ▪ Post-op evaluation LAB RESULTS ▪ Increased maternal serum alphafetoprotein (MSAFP) OTHER DIAGNOSTICS Figure 37.1 An abdominal X-ray of a newborn with gastroschisis. The abdominal contents are clearly visible outside the abdominal wall. ▪ Defect visible at birth TREATMENT ▪ Fatal if untreated MEDICATIONS ▪ Antibiotics for existing/potential infection ▪ IV ﬂuid/nutrients SURGERY ▪ Surgical repositioning of organs back into abdominal cavity, closure of abdominal wall defect ▪ Usually requires multiple surgeries OSMOSIS.ORG 317
HIRSCHSPRUNG'S DISEASE osms.it/hirschsprungs-disease PATHOLOGY & CAUSES ▪ Myenteric (Auerbach), submucosal (Meissner) plexuses absent from intestinal wall in distal bowel ▪ AKA congenital aganglionic megacolon ▪ Absent plexuses (regulate bowel function) → intestine muscles permanently constricted → passing stool difﬁcult, impossible CAUSES ▪ Failure of neuroblasts to migrate from neural crest to intestine, form plexuses ▪ Genetic: RET proto-oncogene, EDNRB, etc. ▪ RET proto-oncogene: sporadic/autosomal dominant (familial) cases; associated with Down syndrome ▪ Isolated: sporadic/autosomal dominant ▪ Present within syndrome: Down syndrome, multiple endocrine neoplasia II, etc. DIAGNOSIS DIAGNOSTIC IMAGING ▪ Barium assisted radiography LAB RESULTS ▪ Rectal suction biopsy OTHER DIAGNOSTICS ▪ Digital rectal exam TREATMENT SURGERY ▪ Surgical resection of intestine, subsequent fusion of remaining healthy tissue (pullthrough technique) COMPLICATIONS ▪ Constipation/obstipation, malnutrition, enterocolitis, intestinal perforation, megacolon SIGNS & SYMPTOMS ▪ At birth: asymptomatic ▪ Can be diagnosed in adulthood ▪ First sign: baby’s inability to pass meconium, 48 hours postpartum ▪ Vomiting, abdominal distension, colics 318 OSMOSIS.ORG Figure 37.2 Immunohistochemical staining for acetylcholinesterase in the colon of an individual with Hirschprung’s disease. Ganglia are absent resulting in overstimulation of nerves and increased levels of acetylcholinesterase.
Chapter 37 Lower Gastrointestinal Congenital Malformations IMPERFORATE ANUS osms.it/imperforate-anus DIAGNOSIS PATHOLOGY & CAUSES ▪ Narrowed anal opening (anal stenosis)/ complete atresia ▪ AKA anal atresia ▪ Anus completely closed → colon ends in blind pouch in pelvis/opens into other pelvic structures (bladder, vagina) via ﬁstulae ▪ All pelvic structures open into same channel → persistent cloaca ▪ Nerve, muscle tissue of missing parts of anus, rectum missing/malformed DIAGNOSTIC IMAGING CAUSES SURGERY ▪ Mostly unknown genetic cause ▪ HLXB9 gene: only when imperforate anus is present within Currarino syndrome MRI, ultrasound, X-ray/CT scan ▪ Determine internal extent of defect, plan corrective surgery OTHER DIAGNOSTICS ▪ Physical exam at birth, defect visible TREATMENT ▪ Anoplasty if possible, colostomy if not COMPLICATIONS ▪ Megacolon, intestinal rupture, septic shock, incontinence/constipation (even after surgery) MNEMONIC: VACTERL Group of malformations with common, unknown cause Vertebral anomalies Anal atresia Cardiovascular anomalies Tracheoesophageal ﬁstula Esophageal atresia Renal anomalies Limb defects Figure 37.3 A lateral X-ray of a neonate demonstrating an imperforate anus. The rectum is dilated and the anal canal is absent. SIGNS & SYMPTOMS ▪ Constipation (if anus narrowed), obstipation (if anus non-existent) ▪ Vomiting, abdominal distension OSMOSIS.ORG 319
INTESTINAL ATRESIA osms.it/intestinal-atresia PATHOLOGY & CAUSES ▪ Congenital malformation resulting in closed/ absent part of small/large intestine ▪ Different from intestinal stenosis; in stenosis the passageway exists, and is just narrowed TYPES ▪ Named according to affected portion of intestine: duodenal, jejunal, ileal, colonic ▪ Divided into duodenal/non-duodenal intestinal atresia due to different mechanism of origin ▪ Duodenal intestinal atresia is caused by failure in duodenal vacuolization ▫ During fetal development duodenal epithelium proliferates rapidly → complete duodenal obstruction (AKA solid phase of vacuolization)→ apoptosis of excess cells → formation of small vacuoles which fuse → reestablish duodenal passageway (AKA recanalization phase) CAUSES ▪ Duodenal intestinal atresia ▫ Strongly associated with trisomy 21 (Down syndrome) ▪ Non-duodenal intestinal atresias ▫ Intrauterine ischemic injury (small part of duodenum, entire jejunum, ileum, colon receive vascularization from superior mesenteric artery) COMPLICATIONS ▪ Distension of stomach and duodenum caused by accumulated amniotic ﬂuid which has nowhere to go ▪ Polyhydramnios (accumulation of amniotic ﬂuid in amniotic sac) ▫ Fetus swallows less ﬂuid due to intestinal obstruction → more ﬂuid accumulates in amniotic sac ▪ Intestinal perforation and pneumoperitoneum/meconium peritonitis SIGNS & SYMPTOMS ▪ Bilious vomiting, abdominal pain, malnutrition 320 OSMOSIS.ORG
Chapter 37 Lower Gastrointestinal Congenital Malformations DIAGNOSIS DIAGNOSTIC IMAGING Prenatal ultrasound ▪ To assess signs of obstruction; detectable in the third trimester ▫ Duodenal atresia: dilated ﬂuid-ﬁlled stomach adjacent to dilated duodenum ▫ Non-duodenal intestinal atresia: Dilated ﬂuid-ﬁlled bowel loops ▫ Polyhydramnios Postnatal X-ray ▪ Duodenal atresia: Double bubble sign (dilated stomach adjacent to dilated duodenum) ▪ Non-duodenal intestinal atresia: dilated bowel loops with air-ﬂuid levels proximal to the obstruction Figure 37.5 A plain abdominal radiograph of a neonate demonstrating the double bubble sign of duodenal atresia. OTHER DIAGNOSTICS ▪ Physical examination ▫ Apple peel (spiral) shape of intestines upon visual examination during surgery ▪ Amniocentesis to determine possible trisomy 21 TREATMENT SURGERY ▪ Gastric decompression: removal of ﬂuid from stomach ▪ IV ﬂuid compensation ▪ Surgical reattachment of functional portions of intestines ▫ In case of duodenal intestinal atresia → duodenoduodenostomy Figure 37.4 A plain abdominal radiograph of a neonate demonstrating the triple bubble sign of jejunal atresia. OSMOSIS.ORG 321
INTESTINAL MALROTATION osms.it/intestinal-malrotation DIAGNOSIS PATHOLOGY & CAUSES ▪ Improper rotation of midgut during embryogenesis ▪ Rapid midgut growth in restricted space → herniation into umbilical coelum → rotation 270° around SMA → error occurs = ﬁnal anatomy description ▫ Small intestine lodges into left abdominal cavity → cecum in lower right quadrant, ﬁrst two thirds of colon lodge into right side over small intestine ▪ Due to error, several organs in incorrect anatomical position ▫ Small intestine in right side ▫ Coecum in epigastrium ▫ Appendix follows coecum ▫ Ladd’s bands span over vertical duodenum, compressing from outside ▫ Suspensory muscle of duodenum further right ▫ Mesentery of small intestine narrower root DIAGNOSTIC IMAGING MRI/CT scan/barium-assisted radiography ▪ Detect improper organ position TREATMENT SURGERY ▪ Surgical repositioning of intestines, resection of Ladd’s bands to remove duodenal obstruction ▪ Preventive appendectomy COMPLICATIONS ▪ Omphalocele, volvulus (part of intestine rotates around itself/part of mesenterium → blocks passage of intestinal content → compresses blood vessels → obstructs blood ﬂow), ileus, ischemic bowel, malnutrition, hernias SIGNS & SYMPTOMS ▪ May be asymptomatic ▪ Colic, bilous regurgitation, abdominal distension 322 OSMOSIS.ORG Figure 37.6 An abdominal X-ray with bowel contrast demonstrating intestinal malrotation. The entire small bowel is situated on the right side of the abdomen.
Chapter 37 Lower Gastrointestinal Congenital Malformations MECKEL'S DIVERTICULUM osms.it/meckels-diverticulum DIAGNOSIS PATHOLOGY & CAUSES ▪ Abnormal pouch on antimesenteric side of ileum ▪ True diverticulum (contains all three layers of intestinal wall) ▪ Early fetal life: nutrients received from yolk sac into ileum via omphalomesenteric duct until it obliterates (week 5–6 of pregnancy) ▪ If omphalomesenteric duct obliterates improperly: Meckel’s diverticulum ▪ May contain ectopic epithelia, omphalomesenteric duct lined with pluripotent cells COMPLICATIONS ▪ Diverticulitis, ulcers from HCl secretion if gastric mucosa present, perforation of diverticulum, food impaction, lithiasis, peritonitis, peritoneal adhesions, intussusception, volvulus, neoplasms MNEMONIC DIAGNOSTIC IMAGING Abdominal ultrasound/CT scan ▪ Incidental ﬁnding Angiography OTHER DIAGNOSTICS Meckel’s scan ▪ In children; technetium-99m procedure, detects gastric mucosa in diverticulum Surgery ▪ Incidental ﬁnding TREATMENT SURGERY ▪ Uncomplicated: resection of diverticulum ▪ Complicated: resection of diverticulum, intestine Meckel's Rule of 2s Symptomatic presentation before 2 years of age 2% of population Approximately 2 feet from ileocecal valve 2 inches in length 2 types of ectopic mucosa (pancreatic, gastric) SIGNS & SYMPTOMS ▪ Usually asymptomatic ▪ Abdominal pain/distension, melena, vomiting, constipation Figure 37.7 Intraoperative photograph of a Meckel’s diverticulum. OSMOSIS.ORG 323
Figure 37.8 A CT scan in the axial plane demonstrating a Meckel’s diverticulum. Figure 37.9 Histological appearance of a Meckel’s diverticulum containing ectopic gastric mucosa. 324 OSMOSIS.ORG
Chapter 37 Lower Gastrointestinal Congenital Malformations OMPHALOCELE osms.it/omphalocele DIAGNOSIS PATHOLOGY & CAUSES ▪ Persistent, pathological, herniation of intestines into umbilical cord ▪ Midgut herniates through umbilicus → pulls layer of peritoneum into umbilical cord in order to properly develop (grow, rotate) due to insufﬁcient space in abdominal cavity → returns into abdomen ▪ Midgut doesn’t return: omphalocele ▪ High mortality rate DIAGNOSTIC IMAGING Intrauterine ultrasound MRI LAB RESULTS ▪ Blood test for MSAFP ▪ Amniocentesis TREATMENT CAUSES ▪ Genetic, environmental factors ▪ Associated with: trisomy 13 (Patau syndrome), trisomy 18 (Edward’s syndrome), trisomy 21 (Down syndrome), Beckwith–Wiedemann syndrome SURGERY ▪ Surgical repositioning of protruding organs RISK FACTORS ▪ Consumption of alcohol/tobacco during pregnancy, certain medications (SSRIs), obesity COMPLICATIONS ▪ Abdominal cavity malformation, volvulus, ischemic bowel SIGNS & SYMPTOMS ▪ Intrauterine: asymptomatic ▪ At birth: visible defect Figure 37.10 An MRI scan in the sagittal plane demonstrating a large omphalocele. The abdominal organs are clearly visible outside the abdominal wall. OSMOSIS.ORG 325
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