Spectrum of Clinicopathological Deviations in Long-Segment Hirschsprung Disease Compared With Short-Segment Hirschsprung Disease: A Single-Institution Study

Hirschsprung's disease. Management

BACKGROUND

Hirschsprung's disease (HD) is a rare congenital disease that is characterised by the absence of ganglion cells in the myenteric plexus starting in the distal bowel. This results in distal functional obstruction and may lead to complications like enterocolitis. The treatment is surgical and requires the resection of the aganglionic segment, and the pull-through of normal intestine into the anal opening. However, even after successful surgery, patients may continue to have symptoms.

AIM

Discuss current surgical techniques and management strategies for patients with postoperative symptoms after surgical correction of Hirschsprung's disease.

METHODS

A review of the literature was done through PubMed, with a focus on clinical management and approach.

RESULTS

We describe the clinical problems that can occur after surgical correction. These include obstructive symptoms, enterocolitis, or faecal incontinence. A systematic approach for the evaluation of these patients includes the exclusion of anatomic, inflammatory, behavioural or motility related factors. Depending on the severity of the symptoms, the evaluation includes examination under anaesthesia, the performance of contrast studies, endoscopic studies, measurement of anal sphincter function and colonic motility studies. The treatment is focused towards addressing the different pathophysiological mechanisms, and may include medical management, botulinum toxin to the anal sphincter or rarely redo-operation.

CONCLUSIONS

Patients with Hirschsprung's disease need to have surgical correction, and their postoperative long-term management is complex given a variety of associated problems that can occur after surgery. A systematic evaluation is necessary to provide appropriate therapy.

Hirschsprung disease

Hirschsprung disease (HSCR) is a rare congenital intestinal disease that occurs in 1 in 5,000 live births. HSCR is characterized by the absence of ganglion cells in the myenteric and submucosal plexuses of the intestine. Most patients present during the neonatal period with the first meconium passage delayed beyond 24 h, abdominal distension and vomiting. Syndromes associated with HSCR include trisomy 21, Mowat-Wilson syndrome, congenital central hypoventilation syndrome, Shah-Waardenburg syndrome and cartilage-hair hypoplasia. Multiple putative genes are involved in familial and isolated HSCR, of which the most common are the RET proto-oncogene and EDNRB. Diagnosis consists of visualization of a transition zone on contrast enema and confirmation via rectal biopsy. HSCR is typically managed by surgical removal of the aganglionic bowel and reconstruction of the intestinal tract by connecting the normally innervated bowel down to the anus while preserving normal sphincter function. Several procedures, namely Swenson, Soave and Duhamel procedures, can be undertaken and may include a laparoscopically assisted approach. Short-term and long-term comorbidities include persistent obstructive symptoms, enterocolitis and soiling. Continued research and innovation to better understand disease mechanisms holds promise for developing novel techniques for diagnosis and therapy, and improving outcomes in patients.

A Novel Method for Identifying the Transition Zone in Long-Segment Hirschsprung Disease: Investigating the Muscle Unit to Ganglion Ratio

Hirschsprung disease (HSCR) is characterised by the absence of enteric ganglia along variable lengths of the distal bowel. Current gold standard treatment involves the surgical resection of the defective, aganglionic bowel. Clear and reliable distinction of the normoganglionated bowel from the transition zone is key for successful resection of the entire defective bowel, and the avoidance of subsequent postoperative complications. However, the intraoperative nature of the tissue analysis and the variability of patient samples, sample preparation, and operator objectivity, make reproducible identification of the transition zone difficult. Here, we have described a novel method for using muscle units as a distinctive landmark for quantifying the density of enteric ganglia in resection specimens from HSCR patients. We show that the muscle unit to ganglion ratio is greater in the transition zone when compared with the proximal, normoganglionated region for long-segment HSCR patients. Patients with short-segment HSCR were also investigated, however, the muscle unit to ganglion ratio was not significantly different in these patients. Immunohistochemical examination of individual ganglia showed that there were no differences in the proportions of either enteric neurons or glial cells through the different regions of the resected colon. In addition, we identified that the size of enteric ganglia was smaller for patients that went on to develop HSCR associated enterocolitis; although the density of ganglia, as determined by the muscle unit to ganglia ratio, was not different when compared with patients that had no further complications. This suggests that subtle changes in the enteric nervous system, even in the “normoganglionated” colon, could be involved in changes in immune function and subsequent bacterial dysbiosis.

Hirschsprung's Disease-Recent Understanding of Embryonic Aspects, Etiopathogenesis and Future Treatment Avenues

Hirschsprung's disease is a neurocristopathy, caused by defective migration, proliferation, differentiation and survival of neural crest cells, leading to gut aganglionosis. It usually manifests rapidly after birth, affecting 1 in 5000 live births around the globe. In recent decades, there has been a significant improvement in the understanding of its genetics and the association with other congenital anomalies, which share the pathomechanism of improper development of the neural crest. Apart from that, several cell populations which do not originate from the neural crest, but contribute to the development of Hirschsprung's disease, have also been described, namely mast cells and interstitial cells of Cajal. From the diagnostic perspective, researchers also focused on "Variants of Hirschsprung's disease", which can mimic the clinical signs of the disease, but are in fact different entities, with distinct prognosis and treatment approaches. The treatment of Hirschsprung's disease is usually surgical resection of the aganglionic part of the intestine, however, as many as 30-50% of patients experience persisting symptoms. Considering this fact, this review article also outlines future hopes and perspectives in Hirschsprung's disease management, which has the potential to benefit from the advancements in the fields of cell-based therapy and tissue engineering.

Thyroid Hormone in the Pathogenesis of Congenital Intestinal Dysganglionosis

INTRODUCTION

The objective of this study is to investigate the role of thyroid hormone (TH) in the pathogenesis of intestinal dysganglionosis (ID).

METHODS

A zebrafish model of congenital hypothyroidism (CH) was created by exposing the larvae to the 6-propyl-2-thiouracil (PTU). The enteric neurons were labeled with anti-HuC/D antibodies. The number of enteric neurons was counted. The larval intestine was dissociated and stained with anti-p75 and anti-α4 integrin antibodies. Mitosis and apoptosis of the p75⁺ α4 integrin⁺ enteric neural crest cells (ENCCs) were studied using flow cytometry. Intestinal motility was studied by analyzing the transit of fluorescent tracers.

RESULTS

PTU (25 mg/L) significantly reduced TH production at 6- and 9-days post fertilization without changing the body length, body weight, and intestinal length of the larvae. Furthermore, PTU inhibited mitosis of ENCCs and reduced the number of enteric neurons throughout the larval zebrafish intestine. Importantly, PTU inhibited intestinal transit of fluorescent tracers. Finally, thyroxine supplementation restored ENCC mitosis, increased the number of enteric neurons, and recovered intestinal motility in the PTU-treated larvae.

CONCLUSIONS

PTU inhibited TH production, reduced the number of enteric neurons, impaired intestinal motility, and impeded ENCC mitosis in zebrafish, suggesting a possible role of CH in the pathogenesis of ID.

Transition Zone in Total Colonic Aganglionosis and Colorectal Hirschsprung's Disease Shows a Similar Trend of Mucosal Innervation: Image Processing and Analysis Study

The aganglionic segment of bowel in Hirschsprung's disease (HD) varies in length. It is not clear whether total colonic aganglionosis (TCA) merely represents a long form of HD or a different phenotype of the disease. Animal model studies suggest that TCA may have a longer transition zone (TZ) than conventional colorectal HD. We compared mucosal innervation of TZ in 2 TCA cases and 10 conventional colorectal HD cases by quantifying calretinin-positive mucosal nerve fibers using image processing and analysis. One TCA was associated with esophageal atresia-tracheoesophageal fistula, the other with trisomy 21. The gradients of calretinin-stained pixel count increase per distance from the beginning of TZ (slope) for TCA were not significantly different from those for the conventional HD group. Given this observation, it is speculated that the length of TZ in TCA may fall within the range of and may not be much longer than conventional colorectal HD.

Hirschsprung disease: Insights on genes, penetrance, and prenatal diagnosis

The objective of this mini-review is to provide insights on the advances in the understanding of the genetic variants associated with different manifestations of Hirschsprung disease, which may present with a range of denervation from a short segment of colon to total colonic and small bowel or extensive aganglionosis. A recent article in this journal documented potential gene variants involved in long-segment Hirschsprung disease in 23 patients. Gene variants were identified using a 31-gene panel of genes related to Hirschsprung disease or enteric neural crest cell development, as previously reported in the literature. The study identified potentially harmful variants in eight genes across 13 patients, with a detection rate of 56.5% (13/23 patients). Five patients had pathologic variants in RET, NRG1, and L1CAM, and the remainder were considered variants of unknown significance. The authors attempted prenatal diagnosis of Hirschsprung disease utilizing an amniocentesis sample obtained for advanced maternal age in a family with a known deleterious RET mutation, manifested in the father (long-segment Hirschsprung disease) and older daughter (total colonic aganglionosis). The fetus had the same RET variant but, after several years of follow-up, has not developed any symptoms of Hirschsprung disease, supporting the conclusion that this RET mutation is an autosomal dominant gene with incomplete penetrance. This experience suggests that genetic counseling is appropriate to carefully assess the justification of prenatal testing, especially, when the phenotype of long-segment Hirschsprung disease is so variable and the disease is potentially curable with surgery.