Histology of the myenteric plexus in relation to rectal biopsy in congenital megacolon

Biopsy Diagnosis of Hirschsprung's Disease Using a Single Excisional Biopsy Based on the Anorectal Line

INTRODUCTION

 A biopsy protocol for diagnosing Hirschsprung's disease (HD) in children using the anorectal line (ARL).

MATERIALS AND METHODS

 The ARL was adopted for diagnosing HD in 2016 using two excisional submucosal rectal biopsies performed at different levels, sequentially; the first just above the ARL and the second, further proximal (2-ARL). Currently, only the first-level biopsy is performed (1-ARL) and examined intraoperatively. Management was observation if normoganglionic, pull-through if aganglionic, and a second-level biopsy if hypoganglionic. Hypoganglionosis was considered physiologic if the second-level biopsy was normoganglionic and pathologic if hypoganglionic. Colon caliber change and bowel obstructive symptoms reflect the severity of hypoganglionosis.

RESULTS

 For 2-ARL (n = 54), results were: normoganglionosis (n = 31/54; 57.4%), aganglionosis (n = 19/54; 35.2%), and hypoganglionosis (n = 4/54; 7.4%); physiologic (n = 3/54; 5.6%) and pathologic (n = 1/54; 1.9%). Normoganglionosis and aganglionosis were always duplicated in 2-ARL (kappa = 1.0). For 1-ARL (n = 36), results were: normoganglionosis (n = 17/36; 47.2%), aganglionosis (n = 17/36; 47.2%), and hypoganglionosis (n = 2/36; 5.6%). Second-level biopsies were normoganglionic (physiologic: n = 1) and hypoganglionic (pathologic: n = 1). All normoganglionic cases, except one, resolved conservatively. All aganglionic cases had pull-through with HD confirmed on histopathology. Both pathologic hypoganglionic cases had caliber change and severe obstructive symptoms as definitive indications for pull-through with hypoganglionosis of the entire rectum confirmed on histopathology. Physiologic hypoganglionic cases were observed and currently have regular defecation.

CONCLUSION

 Because the ARL is an objective functional, neurologic, and anatomic demarcation, normoganglionosis and aganglionosis can be diagnosed accurately with a single excisional biopsy. Only hypoganglionosis requires a second-level biopsy.

Are We Underdiagnosing Hirschsprung Disease?

Hirschsprung disease (HSCR) is conventionally defined as aganglionosis of the distal rectum and a variable length of proximal contiguous bowel with a transition zone of ganglionic, but neuroanatomically abnormal, bowel located immediately upstream. Recent improvement in our understanding of the pathology and genetics of HSCR and relevant animal models indicates highly variable expressivity. The spectrum of intestinal neuropathology includes patients with very short-segment aganglionosis, limited to the distal 1 to 2 cm of the rectum, and possibly patients with no true aganglionic segment, but nonphysiological transition zone pathology in their distal rectums. The presence or absence of submucosal ganglion cells in a rectal biopsy is not sufficient to exclude these patients, in whom submucosal nerve hypertrophy and/or abnormal cholinergic mucosal innervation may be the only diagnostic clues. In addition, diagnosis or exclusion of HSCR by rectal biopsy now relies in part on mucosal patterns of calretinin immunohistochemistry, with less emphasis on submucosal tissue adequacy and assessment of cholinergic innervation. These recent trends in the surgical pathology approach to rectal biopsies may miss patients at the phenotypically milder end of the malformation spectrum, with profound implications for subsequent management, prognosis, and genetic counseling.

Diagnosis of Hirschsprung Disease

Diagnosis or exclusion of Hirschsprung disease (HSCR) is a frequent exercise in any pediatric hospital. Although HSCR may present at different ages and with varied clinical findings, the most common presentation is a neonate with severe constipation or signs of intestinal obstruction. A variety of diagnostic tests including contrast enema and anorectal manometry may be used as diagnostic screens, but diagnosis ultimately rests upon histopathological evaluation of a rectal biopsy. For the experienced pathologist, conventional hematoxylin-and-eosin-stained sections often suffice to exclude HSCR or establish the diagnosis. However, ancillary diagnostic tests such as acetylcholinesterase histochemistry or calretinin immunohistochemistry are complementary and extremely helpful in some cases. In this Perspectives article, we review the clinical and pathological features of HSCR, highlight those that are found in most patients, and discuss how to address particularly challenging aspects of the diagnostic workup.

Clinical features' diagnostics and treatment of Hirschsprung's disease in adults

AIM

Hirschsprung's disease first diagnosed in adulthood is symptomatic from early childhood in most cases. However, the condition is frequently masked when constipation is managed effectively by enemas and aperients. One third of the patients will experience progressive symptoms or complications, requiring urgent surgical intervention.

METHOD

Ninety patients with adult Hirschsprung's disease were observed by a combination of investigations: barium enema, anorectal physiology, estimation of acetylcholinesterase activity and a 60mm full-thickness strip biopsy. The latter two modalities were performed in selected patients where there was diagnostic uncertainty. Single-staged resections, mostly modified Duhamel procedures, were performed in patients who were stable and fit, and with only a limited degree of megacolon present, and no other complications. Otherwise patients were temporarily defunctioned prior to staged resection. All patients underwent surgical treatment. Long-term functional outcomes were expressed as good, satisfactory or poor.

RESULTS

Median age was 24.5 years, range 14-47 years, and 72.2% were men. Almost three quarters (73.3%) of the patients had symptoms dating from early childhood. Barium enema was diagnostic in 84.3%, and 36.2% had a positive, but weak rectoanal inhibitory reflex. Acetylcholinesterase staining was positive in 85.7%, but full-thickness strip biopsy was positive in 100% of equivocal cases. A separate cadaveric study of unaffected individuals determined the true length of the normal physiological hypoganglionic zone, mean 24.4 mm and range 7.5-50 mm. Supra-anal short segment Hirschprung's disease was found in 5.6% patients, rectal involvement in 54.4%, rectosigmoid in 38.9% and total aganglionosis of the colon in 1.1%. Resection of the aganglionic zone and proximally dilated colon was performed as a single-staged procedure in 67.8%. Staged surgery was carried out in 32.2%. A modified Duhamel procedure was performed in 91.2% of cases. A good or satisfactory functional outcome was achieved in 96.7%. Long-term functional outcome after resection depends on the degree of preoperative megacolon present. Megacolon limited to the sigmoid colon was associated with a good outcome in 89.7%, but in only 66.7% with more proximal dilatation (P < 0.05).

CONCLUSION

Occasionally, Hirschsprung's disease presents in adulthood, with ongoing symptoms from early childhood or with the development of functional obstruction, faecal impaction and megacolon in later life. Diagnosis often requires multimodal investigation. A 60 mm full-thickness strip biopsy confirms aganglionosis in 100%. A modified Duhamel procedure is the operation of choice.

Pelvic floor: anatomy and function

The pelvic floor is a dome-shaped striated muscular sheet that encloses the bladder, uterus, and rectum, and, together with the anal sphincters, has an important role in regulating storage and evacuation of urine and stool. This article reviews the anatomy, nerve supply, pharmacology, and functions of the anal sphincters and the pelvic floor. The internal and external anal sphincters are primarily responsible for maintaining faecal continence at rest and when continence is threatened, respectively. Defecation is a somato-visceral reflex regulated by dual nerve supply (i.e. somatic and autonomic) to the anorectum. The net effects of sympathetic and cholinergic stimulation are to increase and reduce anal resting pressure, respectively. Faecal incontinence and functional defecatory disorders may result from structural changes and/or functional disturbances in the mechanisms of faecal continence and defecation.

An experimental study on the mechanism of rectosphincteric reflex in special reference to Hirschsprung's disease

In order to clarify the mechanism of rectosphincteric reflex (RSR), an experimental study was performed using mongrel canine models. The RSR exists in normal anesthetized mongrel dogs. It does not disappear in dogs with isolation of the rectoanal portion from the surrounding tissues. The RSR disappeared after circular transection of the rectal muscle coat at the level between the rectum and the anal canal, and also after selective destruction of the myenteric plexus of the rectum. These data suggest that the RSR is a local reflex contained within the rectoanal wall and its regulating center and neural pathway are in the myenteric plexus of the rectum.

Histologic studies of rectocolic aganglionosis and allied diseases

It is well-known that some patients exhibiting the symptoms of Hirschsprung's disease are shown to have intramural ganglia in the distal myenteric plexus. Some of them have been described as "pseudo-Hirschsprung's disease". It is likely that a variety of conditions have been included in this group. Using a silver impregnation technique we have made a detailed histologic study of the rectum and large bowel in a number of cases with provisional clinical diagnosis of Hirschsprung's disease but in which rectal biopsy showed small ganglia in Meissner's plexus demonstrated by acetylcholinesterase (Ach-E) staining. Three histologic variations were shown that may be called hypoganglionosis, immaturity of ganglia, and hypogenesis. An attempt is made to relate their clinical picture to the histologic findings.

Adrenergic innervation of bowel in Hirschsprung's disease

The adrenergic innervation of normal and aganglionic regions of bowel from patients with Hirschsprung's disease was investigated by a fluorescent histochemical technique. In normal bowel the adrenergic nerves end about intramural ganglion cells. In aganglionic bowel the adrenergic nerves form a dense varicose plexus in both muscularis externa and muscularis mucosae. It is suggested that the cause of megacolon in Hirschsprung's disease is due to a lack of nervous pathways controlling the intrinsic reflexes, which is probably congenital in origin.