Total Intestinal Aganglionosis with a Segment of Dysganglionosis in the Submucosa of Proximal Jejunum
Hirschsprung disease (HSCR), characterized by congenital absence of ganglion cells from the distal rectum and a variable length of contiguous bowel, affects an estimated 1 in 5000 newborns (Kapur 2016) . In 80% of cases, the aganglionic segment is limited to rectum and distal sigmoid colon (short segment HSCR). In other cases, the aganglionic segment extends beyond the splenic flexure to variable lengths (long segment HD) . Total intestinal aganglionosis is the rarest and most severe form of HSCR and represents about 1% of HSCR cases . This case is an example of total intestinal aganglionosis with hypoganglionosis in stomach.
Skip segment Hirschsprung disease (SSHD) refers to a focal area of normally ganglionated bowel (skip segment) flanked by aganglionosis proximally and distally. SSHD is different from zonal aganglionosis, which means a focal area of aganglionosis flanked by ganglionated bowel proximally and distally [4,5]. SSHD is a rare phenomenon and can cause confusion while interpreting biopsies taken to assess the site of an anastomosis during corrective surgery (bowel pull-through) .
In this case, the segment of proximal jejunum shows multiple clusters of submucosal ganglion cells but a total absence of myenteric ganglion cells. Therefore it is not really a SSHD, which by definition requires the segment to be normally ganglionated. This segment likely represents an area of dysganglionosis similar to the so-called transition zone, although it is different from the latter because it is flanked by two areas of aganglionosis. This phenomenon is not well described in the medical literature, but as illustrated in this case, its presence can also impact surgical management significantly. In particular, if only a suction rectal mucosal biopsy were performed and only H&E stain were used, this segment would look like normally ganglionated bowel.
Transition zone of HSCR generally refers to a length of ganglionic bowel, immediately proximal to the aganglionic segment, with neuropathologic features that correlate with dysmotility . It is a transition area between the more distal aganglionic bowel and the proximal normally ganglionated bowel. The common histopathological features of transition zone include partial circumferential aganglionosis (absence of ganglion cells around part of the bowel circumference), myenteric hypo- or hyperganglionosis and submucosal nerve hypertrophy . Most (but not all) transition zones are less than 5 cm in length. In this case, the proximal jejunum is not really a "transition zone" by its classical definition but rather a segment of partially and abnormally ganglionated bowel flanked by completely aganglionic segments both proximally and distally.
Calretinin immunohistochemistry is a reliable ancillary method to help in the diagnosis HSCR. In normally ganglionated bowel, positively stained fine nerve fibers, and depending on the depth of the biopsy, ganglion cells and nerves are found in submucosal and myenteric plexus. In addition, positively stained nerve fibers are also present in muscularis mucosae and lamina propria, as shown in Figure 7. Absence of staining favors a diagnosis of HSCR . In this case, calretinin immunostain of the proximal jejunum section does not show calretinin-positive nerve fibers, further supporting the notion that this segment of small bowel is not normal and shows dysganglionosis.
One of the diagnostic features of HSCR is the presence of hypertrophic extrinsic nerve fibers (both autonomic and sensory) in the myenteric and submucosal plexus. The presence of nerve trunks > 40 microns in diameter in the submucosa has a statistically significant correlation with the diagnosis of HSCR in mucosal/submucosal rectal suction biopsies . This feature is useful in the diagnosis of short segment (classic) HSCR and not in long segment HSCR. Long segment HSCR usually features hypertrophic nerve trunks only in rectosigmoid colon, and these trunks are absent in more proximal areas [8,9]. In this case, there are occasional large nerve trunks in the myenteric plexus throughout the intestinal tract, but no hypertrophic nerve trunks are identified in the submucosa. Hypertrophic nerve trunks can also be highlighted by Glut-1 staining .
Another useful ancillary diagnostic method is acetylcholinesterase (AChE) histochemical staining. The extrinsic parasympathetic nerve fibers in HSCR show much stronger AchE activity than nerve fibers in normal intestine. Since this technique is based on an enzymatic reaction it requires frozen section slides. In mucosal/submucosal biopsies of normally ganglionated colon, the AChE-positive fibers are sparse and thin, present in submucosa and in the deeper half of muscularis mucosae only . In contrast, in HSCR, increased numbers of coarse ropey AchE-positive nerve fibers are seen in submucosa and in the entire thickness of the muscularis mucosae (Figure 10, from another HSCR patient). Lamina propria staining may also be seen , especially after 6 months of age. In long segment HSCR, the extrinsic innervation becomes very sparse in the more proximal segments so the AChE staining may not be helpful [8,10]. Therefore, AChE histochemical staining was not used in this case.
Finally, a useful technique to quickly assess the presence of ganglion cells during intraoperative frozen sections is the use of Diff-Quik« stain. This fast staining method highlights ganglion cells as a bright, intense blue/violet (azure-like) color (Figure 11) .
Haiying Chen MD, Amy Davis MD and Miguel Reyes-M˙gica MD