Complete innervation profile of whole bowel resected at pull-through for Hirschsprung's disease. Unexpected findings

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.

Surgery, Surgical Pathology, and Postoperative Management of Patients With Hirschsprung Disease

Endorectal pullthrough surgery is integral in the treatment of patients with Hirschsprung disease. Several different surgical procedures exist, which share as common goals to excise the aganglionic segment and upstream transition zone and attach ganglionic bowel just proximal to the anal canal. The operation requires collaboration between surgeon and pathologist to localize ganglionic bowel and prevent retention of transition zone. Intraoperative frozen sections are extremely important, first to establish that ganglion cells are present and subsequently to exclude features of transition zone (partial circumferential aganglionosis, myenteric hypoganglionosis, and submucosal nerve hypertrophy) at the proximal surgical (anastomotic) margin. Postoperative histopathological analysis of resection specimens should be tailored to document distal aganglionosis, document the length of the aganglionic segment and its proximity to the anastomotic margin, and confirm that transition zone has been resected completely. Adherence to the recommendations described in this review will reduce the likelihood of transition zone pullthrough and should decrease the incidence of persistent postoperative obstructive symptoms.

The Extent of the Transition Zone in Hirschsprung Disease

BACKGROUND

Retained transition zone is a leading cause of obstructive symptoms after pull-through operation in Hirschsprung's disease.

OBJECTIVE

We aimed to evaluate the extent of the histological transition zone in patients with Hirschsprung's disease.

DESIGN

We performed an observational study. DAB+ immunohistochemistry for Protein Gene Product 9.5 was used to evaluate the neuronal networks in serial sections of pull-through specimens obtained from children with Hirschsprung's disease (n = 12). Reference ranges for ganglion size/density and nerve trunk diameter were statistically determined using healthy controls obtained from colostomy specimens from children with anorectal malformations (n = 8). The transition zone was defined as ganglionic bowel exhibiting ganglion hypoplasia, hypertrophic nerve trunks, or partial circumference aganglionosis.

RESULTS

The mean submucosal nerve trunk diameter in controls was 19.56 μm +/- 3.87 μm. The median age at pull-through for Hirschsprung's disease was 5 months (3-14 months). The median length of the transition zone across the population was 8 cm (4-22 cm). Median transition zone extent was significantly longer in patients with long-segment aganglionosis (n = 6) compared to rectosigmoid aganglionosis (n = 6, 13 cm vs 6 cm, p = 0.041). Due to the age of the patients enrolled, long-term follow-up of bowel function is not yet available.

CONCLUSION

Our data suggest that, in children with rectosigmoid Hirschsprung's disease, the transition zone can extend for up to 13 cm. In children with long-segment disease, a longer transition zone is possible. Extended resection at a minimum 5 cm beyond the most distal ganglionic intra-operative biopsy and intra-operative histological examination of the proximal resection margin are required to minimize transition zone pull-through.

LEVEL OF EVIDENCE

2.

Submucosal nerve diameter of greater than 40 μm is not a valid diagnostic index of transition zone pull-through

BACKGROUND

Submucosal nerve hypertrophy is a feature of the transition zone in Hirschsprung disease and has been used as a primary diagnostic feature of transition zone pull-through for patients with persistent obstructive symptoms after their initial surgery. Most published criteria for identification of hypertrophy rely on a nerve diameter of greater than 40μm, based primarily on data from a relatively small number of infants with Hirschsprung disease and controls. The validity of these objective measures has not been validated in appropriate controls for post-pull-through patients.

SCIENTIFIC APPROACH

The primary pull-through specimens and post pull-through biopsies +/- redo pull-through resections from a series of 9 patients with Hirschsprung disease were reviewed to assess the prevalence of submucosal nerves >40μm in diameter and 400× microscopic fields containing two or more such nerves. Similar data from multiple colonic locations were collected from a series of 40 non-Hirschsprung autopsy and surgical controls.

RESULTS

The overwhelming majority of Hirschsprung patients harbored submucosal nerves >40μm in their post-pull-through specimens independent of other features of transition zone pathology, and despite normal innervation at the proximal margins of their initial resections. Measurement of submucosal nerve diameters in autopsy and surgical non-Hirschsprung control samples indicated that nerves >40μm are normal in the distal rectum after 1year of age and are found in more proximal colon at older ages.

CONCLUSIONS

These results suggest that diagnostic criteria currently used to recognize submucosal nerve hypertrophy in the neorectum after a pull-through for Hirschsprung disease are not justified and should not be regarded as definitive evidence for transition zone pull-through.

Aganglionosis with the absence of hypertrophied nerve fibres predicts disease proximal to rectosigmoid colon

PURPOSE

The gold standard for the diagnosis of Hirschsprung's disease (HSCR) is the pathologic evaluation of a rectal biopsy that demonstrates the absence of ganglion cells and nerve fibre hypertrophy. However, it has been frequently reported that hypertrophic nerves may not be present in some variants like long-segment HSCR, total colonic aganglionosis, premature and very young infants. The aim of this study was to determine this association.

METHODS

We performed a retrospective review of the HSCR database at our tertiary care children's hospital from 2000 to 2013. In order to analyse the relationship between the diameter of the nerve fibres and the level of aganglionosis, we classified the patient sample into two groups-fibres ≤40 and >40 μm. The groups were statistically compared with P < 0.05 being significant.

RESULTS

Rectal biopsies of 92 patients confirmed as HSCR with definitive operation performed at the same institution were reviewed. The mean nerve diameter was 50.1 μm (range 20-87.5 μm). Nerve fibre diameter ≤40 μm was predictive of transition zone above the sigmoid colon. A specificity of 77.3 % and a likelihood ratio of 2.03 supported this perception. No correlation was noted between nerve fibre diameter and gestational age at birth, birth weight or age at biopsy.

CONCLUSION

The absence of nerve fibre hypertrophy in the presence of aganglionosis on rectal biopsy specimens is predictive of long-segment HSCR.

The neural crest: a versatile organ system

The neural crest is the name given to the strip of cells at the junction between neural and epidermal ectoderm in neurula-stage vertebrate embryos, which is later brought to the dorsal neural tube as the neural folds elevate. The neural crest is a heterogeneous and multipotent progenitor cell population whose cells undergo EMT then extensively and accurately migrate throughout the embryo. Neural crest cells contribute to nearly every organ system in the body, with derivatives of neuronal, glial, neuroendocrine, pigment, and also mesodermal lineages. This breadth of developmental capacity has led to the neural crest being termed the fourth germ layer. The neural crest has occupied a prominent place in developmental biology, due to its exaggerated migratory morphogenesis and its remarkably wide developmental potential. As such, neural crest cells have become an attractive model for developmental biologists for studying these processes. Problems in neural crest development cause a number of human syndromes and birth defects known collectively as neurocristopathies; these include Treacher Collins syndrome, Hirschsprung disease, and 22q11.2 deletion syndromes. Tumors in the neural crest lineage are also of clinical importance, including the aggressive melanoma and neuroblastoma types. These clinical aspects have drawn attention to the selection or creation of neural crest progenitor cells, particularly of human origin, for studying pathologies of the neural crest at the cellular level, and also for possible cell therapeutics. The versatility of the neural crest lends itself to interlinked research, spanning basic developmental biology, birth defect research, oncology, and stem/progenitor cell biology and therapy.

Transitional zone pull through: surgical pathology considerations

Incomplete resection of the transitional zone (TZ) between histologically normal and aganglionic bowel in Hirschsprung disease is a putative cause of postoperative dysmotility. A review of literature indicates that diverse histopathological indexes have been used to define the TZ, and validated and reproducible diagnostic criteria have not been established. As a consequence, the proximal margin of the TZ is difficult to delimit, and the length of the TZ in a given patient depends on the diagnostic criteria used. Seromuscular biopsies are inadequate to exclude TZ, as diagnostic indexes may involve only a portion of the bowel circumference or the submucosa. Most published investigations of postoperative outcome after a TZ pull through (TZPT) conclude that the latter can cause persistent obstructive symptoms, which necessitate reoperation. However, the results of these studies are difficult to translate into clinical practice because most lack appropriate controls, and the overwhelming majority provide inadequate histopathological descriptions for reference at the time of intraoperative frozen section analysis. At present, a conservative approach based on frozen section examination of the entire proximal margin of the resection to exclude obvious subcircumferential aganglionosis (contiguous gap between ganglia of more than one-eighth of the circumference), hypoganglionosis (continuous string of myenteric ganglia comprised of 1 or 2 ganglion cells without surrounding neuropil), or hypertrophic submucosal nerves (>2 nerves with widths ≥40 μm per high-power field) seems prudent. Well-controlled studies to correlate proximal margin histology, especially subtle anatomic or immunohistochemical changes, with postoperative outcome are needed.

Pathology of Intestinal Motor Disorders in Children

Varied intestinal neuromuscular pathologies are responsible for Hirschsprung disease and other forms of chronic pseudo-obstruction that are encountered in pediatrics. Pathologically distinct subtypes discussed in this review include aganglionosis, hypoganglionosis, neuronal intranuclear inclusion disease, ganglionitis, degenerative neuropathy, diffuse ganglioneuromatosis, neuronal dysplasia, malformations of the muscularis propria, degenerative leiomyopathy, leiomyositis, and mitochondriopathies. Emphasis is given to the histopathologic features that distinguish these conditions and their differential diagnoses.

Redo surgery in Hirschsprung disease: what did we learn? Unicentric experience on 70 patients

PURPOSE

This article is aimed at describing a series of 70 patients who underwent a redo pull-through in the period between January 1991 and January 2007 and to compare them with a series of consecutive patients with Hirschsprung disease who underwent a single pull-through.

METHODS

The notes were reviewed, and a comprehensive interview based on a disease-specific questionnaire for continence and quality of life was submitted to all eligible patients. We used a number of consecutive patients who underwent a single pull-through for Hirschsprung disease as control group.

RESULTS

Seventy patients were included. Residual aganglionosis in pulled-through bowel or retained aganglionic rectum represented the indications to reoperation in most cases. Intestinal obstruction represented the leading symptom in more than 60% of patients. We adopted either the endorectal pull-through, the Duhamel, or the Swenson procedure. Thirty-six patients were assessed for long-term outcome. One third experienced complications. Long-term continence was satisfactory in 70%. Enterocolitis, soiling, and perineal excoriations were complained by 30%. Excellent to good perspectives were described by 94%, and excellent to good cosmetic results by 22%. The only significant difference with control group (109 patients) involved cosmetic appearance, whereas soiling, although more frequent, could not be considered significantly increased.

CONCLUSIONS

Patients who experience failure of a pull-through must go through multiple procedures to achieve definitive results. Although overall outcome does not significantly differ from that of a single effective pull-through, great efforts should be made to minimize complications and avoid the need for a redo, which requires experienced surgeons and highly committed families for a longer course of the disease.

Practical pathology and genetics of Hirschsprung's disease

Diagnosis and management of Hirschsprung's disease (HSCR) requires understanding of the malformation's anatomic features and multigenic nature. Rectal biopsies, intraoperative frozen sections, and resection specimens provide invaluable information. Extraction of these data requires thoughtful biopsy technique, adequate histologic sections, histochemistry, and collaboration of surgeon and pathologist. Critical consideration of transition zone anatomy and published studies of "transition zone pull through" indicate that more research is needed to determine how much ganglionic bowel should be resected from HSCR patients. Many HSCR-susceptibility genes have been identified, but mutational analysis has limited practical value unless family history or clinical findings suggest syndromic HSCR.

Variability of acetylcholinesterase hyperinnervation patterns in distal rectal suction biopsy specimens in Hirschsprung disease

Variability in cholinergic innervation may contribute to false-negative and false-positive evaluations for Hirschsprung disease (HD). We compared intraspecimen variability of histochemical acetylcholinesterase (ACE) activity in 62 distal rectal mucosal biopsy specimens from 33 patients with short-segment HD (SSHD), 14 patients with short-segment HD/Down syndrome (SSHD/DS), 10 patients with total colonic aganglionosis (HDTC), and 45 ganglionated control specimens obtained because of clinical suspicion for HD. Specimens were evaluated in 1-mm linear segments for abnormal distribution and abnormal intensity of staining reaction in the lamina propria (LP), muscularis mucosae (MM), numerical excess of small submucosal nerves (SSN), and presence or absence of large submucosal nerves (LSN) defined as >35 microns in diameter. Patients with HD and controls were predominantly infant males. Aggregate length of specimens was 186 mm in HD and 136 mm in controls. We defined multiple patterns and relative frequencies of normal and abnormal ACE reactivity in the muscularis mucosae, submucosal nerves, and innervation in the lamina propria. We verified a hyperinnervation pattern more common in neonates within each subset of HD. Large submucosal nerves >35 microns in diameter are relatively less common in SSHD/DS and HDTC. Eleven of 57 patients with HD had at least 1 mm of normal muscularis mucosae accounting for 19/186 mm examined. Ten percent of control mm had at least 1 submucosal nerve >35 microns in diameter. Intraspecimen variability in ACE patterns, when extreme, can usually be resolved by findings elsewhere in an adequate specimen, minimizing the need for repeat procedures.