Microcolon



Microcolon


Steven J. Kraus, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Meconium Ileus (MI)


  • Jejunoileal Atresia


  • Defunctionalized Colon


  • Immature Colon


Less Common



  • Total Colonic Hirschsprung Disease


  • Omphalomesenteric Duct Remnant Obstruction


  • Ileal Duplication Cyst


  • Colon Atresia


Rare but Important



  • Megacystis Microcolon Intestinal Hypoperistalsis Syndrome


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Patient age (including gestational age)


  • History of ileostomy


  • Family history of bowel disease


  • Caliber of diffusely small colon on contrast enema


  • Appearance of contrast-filled ileum refluxed from enema


Helpful Clues for Common Diagnoses



  • Meconium Ileus (MI)



    • Almost always associated with cystic fibrosis (CF)


    • 1/2 of cases are complicated by perforation, pseudocyst formation, or segmental volvulus


    • 15% of CF patients born with MI


    • Findings of simple meconium ileus



      • Multiple dilated air-filled bowel loops


      • “Soap bubble” densities mid-right lower abdomen


      • Little or no air-fluid levels due to thick meconium


    • Findings of complicated meconium ileus



      • Curvilinear abdominal calcifications (peritoneal, pseudocyst) = meconium peritonitis


      • Soft tissue mass


      • Paucity of bowel gas


    • Contrast enema



      • Microcolon; some say MI causes smallest unused colon


      • Meconium pellets fill small terminal ileum (TI) like “pearls on a string”


      • Dilated ileum proximal to obstructing meconium


      • Rectosigmoid ratio usually normal (> 1)


      • Initially, very little meconium in colon


    • Ultrasound



      • Echogenic bowel loops


      • Meconium pseudocyst ± curvilinear calcifications of wall


      • Peritoneal calcifications


  • Jejunoileal Atresia



    • Microcolon with little or no meconium in distal small bowel, which ends abruptly on neonatal enema


    • Due to in utero ischemic event


    • Multiple dilated air-filled bowel loops


    • Air-fluid levels within bowel loops


    • Gasless abdomen suggests bowel perforation


    • Peritoneal calcifications suggests meconium peritonitis


    • Contrast enema



      • Rectosigmoid ratio > 1


      • Microcolon: More distal the atresia = smaller the microcolon


      • Normal caliber terminal ileum without significant meconium


      • Abrupt termination of refluxed contrast within ileum


    • Proximal jejunal atresia; almost normal-sized colon



      • Succus entericus produced by remaining small bowel flows to colon; therefore, colon becomes normal caliber


  • Defunctionalized Colon



    • Usually clinical history of prior disease requires colostomy



      • Necrotizing enterocolitis (NEC)


      • Bowel perforation


      • Gastroschisis


      • Omphalocele


      • Midgut volvulus with ischemic bowel resection due to malrotation


      • Inflammatory bowel disease (IBD): Crohn or ulcerative colitis


    • Small diameter of colon segment distal to created ostomy on contrast enema or colostogram



      • Caused by disuse; normal diameter usually regained after ostomy takedown



    • Rectosigmoid ratio usually > 1


  • Immature Colon



    • Similar in functional etiology to meconium plug syndrome (MPS), a.k.a. small left colon syndrome


    • Premature infant


    • Normal rectosigmoid ratio


    • Slightly small colon


    • No pathologic diagnosis


    • Sometimes meconium plugs scattered in colon


Helpful Clues for Less Common Diagnoses



  • Total Colonic Hirschsprung Disease



    • a.k.a. total colonic aganglionosis


    • Often involves segment of distal small bowel


    • Rarely aganglionosis involves entire intestine (total intestinal Hirschsprung)


    • Neonatal bowel obstruction


    • Multiple dilated loops of bowel on radiography


    • ± distal ileal small bowel intraluminal calcifications


    • Contrast enema



      • Rectosigmoid ratio > 1


      • Small colon throughout on neonatal contrast enema


      • Findings can sometimes mimic high-transition HD or MPS


      • Colon often shorter than normal


      • Sometimes squared-off flexures


      • Delayed spontaneous evacuation of contrast from colon


  • Ileal Duplication Cyst



    • Small colon due to partial ileal obstruction


    • Normal rectosigmoid ratio (> 1)


    • Well-circumscribed, right lower quadrant fluid collection on US with gut signature


  • Colon Atresia



    • Ischemic event similar to other nonduodenal atresias of small bowel or colon


    • Neonatal bowel obstruction


    • Dilated loop or several loops out of proportion to rest of obstructive pattern on radiograph


    • Microcolon at enema, which terminates at level of colonic atresia


Helpful Clues for Rare Diagnoses

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Aug 10, 2016 | Posted by in PEDIATRICS | Comments Off on Microcolon

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