Hirschsprung's disease overview

# Overview
Hirschsprung's disease involves an enlargement of the colon caused by a bowel obstruction resulting from an aganglionic section of bowel. The condition, in which the normal enteric nerves are absent, begins from the anus and progresses proximally. The length of affected bowel varies, rarely extending more than approximately one foot

# Historical perspective
The disease is named after Harald Hirschsprung, the Danish physician who first described the disease in 1886 when describing two infants who had died with swollen bellies. The autopsies showed identical pictures with pronounced dilatation and hypertrophy of the colon as dominant features.

# Classification
Hirschsprung's disease may be classified as rectosigmoid disease, long segment disease, or ultrashort segment disease based on the extent of colon involvement.

# Pathophysiology
Hirschsprungs disease is a congenital disorder of colon in which certain nerve cells, called ganglion cells, are absent. This may lead to chronic constipation.

# Causes
Hirschsprung's disease is caused by a failure of the myentric and submucosal nerve plexuses to complete craniocaudal migration into the distal colon.

# Differentiating Hirschsprung's diseases from other diseases
Hirschsprung's disease must be differentiated from other diseases that cause meconium pass failure and abdominal distension in infants, such as meconium plug syndrome, small left colon syndrome, or congenital hypothyroidism.

# Epidemiology and Demographics
The incidence of Hirschsprung's disease is 20 per 100,000 newborns. Hirschsprung's disease is three times more common in Asian Americans than the rest of the population. Males are more commonly affected than females.

# Risk Factors
The most potent risk factor for the development of Hirschsprung's disease is a strong family history (i.e. involvement of multiple family members). Other risk factors include a family history of long segment disease and the proband being female.

# Screening
According to the USPSTF, screening is not recommended for Hirschsprung's disease.

# Natural History, Complications, and Prognosis
If left untreated, Hirschsprung's disease can lead to enterocolitis and even death. Common complications include enterocolitis, intestinal perforation, and short bowel syndrome. After appropriate surgical intervention, the odds of mortality drop significantly.

# Diagnosis

## History and Symptoms
Hirschsprung's disease is commonly diagnosed during the neonatal period. The cardinal symptoms of Hirschsprung's disease include abdominal distension, delayed passage of meconium (i.e., after 24-48 hours from birth), and vomiting. 

## Physical Examination
Physical examination is nondiagnostic in newborns. It may reveal a distended abdomen and/or anal spasm. In older children, abdominal distension may result from the inability to release flatus.

## Laboratory Findings
There are no specific laboratory finding associated with Hirschsprung's disease. All the pre-operation blood tests and coagulation tests will be within the reference range.

## X-ray
Abdominal X-ray is the modality of choice in diagnosing Hirschsprung's disease. Major findings on abdominal X-rays in patients affected by Hirschsprung's disease are decreased bowel caliber of the involved segment and colon distension.

## CT Scan
There are no specific CT scan findings associated with Hirschsprung's disease.

## MRI
There are no specific MRI finding associated with Hirschsprung's disease.

## Other Imaging Findings
A barium enema is the mainstay of Hirschsprungs disease diagnosis.

## Other Diagnostic Studies
A rectal biopsy showing the absence of ganglion cells is the only definitive method of diagnosis.

# Treatment

## Medical Therapy
Medical therapy only plays a supportive role in the management of Hirschsprung's disease. Medical therapy indications include preventing disease complications, preventing post-operative infections, and managing post-operative bowel function. Intravenous fluid resuscitation and maintenance, nasogastric decompression, and the administration of intravenous antibiotics (as indicated) remain the cornerstones of initial medical management.

## Surgery
The usual treatment is pull-through surgery, in which the portion of the colon that has nerve cells is pulled through and sewn over the portion that lacks nerve cells (National Digestive Diseases Information Clearinghouse).

## Primary Prevention
There are no primary preventive measures for Hirschsprung's disease.

## Secondary Prevention
To prevent complications of Hirschsprung's disease, diagnosis is required. Secondary preventive measures include the administration of laxatives and antibiotics to prevent obstruction and infection, respectively.