Colon: Evaluation for Hirschsprung Disease



Colon: Evaluation for Hirschsprung Disease










In the normal colon, the myenteric plexus reveals typical ganglion cells with large eccentric nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm image.






In HD, ganglion cells are completely absent from the bowel wall, resulting in the inability of the muscular wall to contract. Nerve fibers image may be hypertrophic, as seen in this submucosal biopsy.


SURGICAL/CLINICAL CONSIDERATIONS


Goal of Consultation



  • Identify appropriate anastomotic site in Hirschsprung disease (HD) pull-through or ostomy takedown operation


  • Establishing diagnosis of HD is best made on permanent suction rectal biopsies



    • Intraoperative consultation for this purpose should be strongly avoided


Change in Patient Management



  • Submit biopsies from the distal-most portion of bowel thought to have normal innervation for frozen section



    • If no ganglion cells are observed, additional (more proximal) biopsies sent until normal colon is identified


    • Additional biopsies are not necessary if tissue is diagnostic of normal bowel


Clinical Setting



  • HD (a.k.a. colonic aganglionosis) results from failure of neural crest cells to colonize entire length of colon



    • Ganglion cells are absent in distal intestine, resulting in inability of colon to contract and relax normally


  • Often presents shortly after birth



    • Failure to pass meconium, abdominal distention, chronic constipation


    • Contrast enema reveals megacolon (proximally) with funnel-shaped transition zone (TZ) and thin distal aganglionic segment


  • Colon can be involved to varying extents



    • Ultrashort segment HD: Distal rectum (terminal 1-4 cm) in ˜ 30% of cases


    • Short-segment HD: Rectosigmoid in ˜ 45% of cases


    • Long-segment HD: Proximal colon to splenic flexure


    • Entire colon: < 10% of cases


    • Zonal colonic aganglionosis (skip-segment HD) is rare


    • Small bowel involvement is rare


  • Aganglionic segment must be resected to restore normal colonic function


SPECIMEN EVALUATION


Gross



  • Full-thickness colonic biopsies or seromuscular biopsies preferred for intraoperative diagnosis



    • Recommended minimum dimensions



      • 1 cm in length


      • 3-5 mm in depth


Frozen Section



  • Orient sections perpendicular to serosal surface



    • Should include entire longitudinal muscular layer and most of circular layer



      • Including both layers is necessary to visualize myenteric plexus


  • Multiple levels of each block should be examined



    • At least 4, up to 10 sections are usually sufficient for evaluation


  • Thicker sections (6 ìm) may be helpful


  • Giemsa or Diff-Quik stains may be easier to interpret



    • Cytoplasm of ganglion cells is stained a contrasting blue color


  • Reliability



    • 3% false-positive diagnoses (nonganglion cells reported as ganglion cells)


    • 3% false-negative diagnoses (true ganglion cells not detected)


Acetylcholinesterase (AChE) Histochemistry



  • Cholinergic nerve fibers of aganglionic colon are more prominent than in normal colon



    • Fibers contain increased amount of AChE


    • Diagnostic features can be seen in superficial layers of colon


  • Rapid technique for AChE has been developed but is only used in some institutions



    • Requires frozen tissue


    • Stains prominent AChE-positive fibers within muscularis mucosa and lamina propria



      • Normal pattern: Absence of fibers or minimal presence in muscularis mucosae or immediately subjacent submucosa



      • Abnormal pattern: Many nerve fibers in muscularis mucosae and extending into lamina propria


MOST COMMON DIAGNOSES


Normal Colon



  • Meissner (submucosal) plexus is located deep to mucosa



    • Ganglion cells are fewer in number in this area


  • Auerbach (myenteric) plexus is located in muscularis plexus



    • Located between longitudinal and circumferential muscularis propria layers


    • Ganglion cells are more abundant and larger


  • Ganglion cells



    • Identified by large size, polygonal shape, abundant eosinophilic cytoplasm, round eccentric nuclei, large eosinophilic nucleoli


    • Organized in neural units



      • 2-10 ganglion cells are arrayed in a semicircle around neural tissue


    • Should be present in normal numbers


  • Normal nerve trunks range: 10-20 ìm



    • Nerve fiber hypertrophy should not be seen


Hirschsprung Disease



  • Absence of ganglion cells in both Meissner and Auerbach plexuses



    • Loss generally correlates between both plexuses


  • Nerve fiber hypertrophy



    • ≥ 40 ìm submucosal nerve fiber diameter in majority of biopsies


    • May not be present when entire colon is involved



      • Nerves may be hypoplastic or absent in this case


Transition Zone (TZ)

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Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Colon: Evaluation for Hirschsprung Disease

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