Megacystis Microcolon Intestinal Hypoperistalsis Syndrome: An Overview

Introduction:

Nutrition and excretion are important functions of the human body. The gastrointestinal tract is responsible for the metabolism of food items, and the urinary tract is responsible for the excretion of metabolic byproducts from the body. Complications affecting both of these systems are rare. Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare genetic disorder that affects both the gastrointestinal tract and urinary tract.

What Is Megacystis Microcolon Intestinal Hypoperistalsis Syndrome?

Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare autosomal recessive disorder. This disorder affects various systems of the human body and causes complications like megacystis (bladder distention in the absence of mechanical obstruction), microcolon (abnormally small colon), and intestinal hypoperistalsis (impaired contraction of intestinal muscles). Apart from this, defective muscle contraction in the urinary tract is also observed. The incidence of this disorder is four times more common in females than in men. The symptoms are found just after the birth.

Pathogenesis:

The pathogenesis of this disorder is not known. Over the years, scientists have identified several genetic factors related to this condition. Associated genes related to this disorder are ACTG2, LMOD1, MYH11, MYL9, and MYLK. 44 percent of cases are related to ACTG2 genetic mutation. This is autosomal dominant in nature. Other genes are autosomal recessive in nature. These genes are responsible for hormonal, myogenic, and neurogenic changes. Smooth muscle of the small intestine shows vacuolar degenerative changes (changes in the nucleus of the muscle fibers). A large amount of connective tissue is present between the smooth muscle cell of the small intestine. Such changes can also be seen in the urinary bladder muscle. Smooth muscles also show excessive glycogen storage capability. Contractility of the smooth muscles is lost due to the absence of cytoskeletal proteins in the smooth muscle layers. Also, smooth muscles show a reduction in the alpha-smooth muscle actin. The interstitial cell of Cajal (a special type of cell present in the gastrointestinal smooth muscles) is absent in such cases in the urinary bladder and intestinal small muscles. In such patients, a reduction in the amount of nicotinic acetylcholine receptors is seen. Also, many patients show decreased amounts of ganglion cells (a type of neural cell). In certain cases, hyperganglionosis (hyperplasia of the submucosal nerve plexus) is observed. The interstitial cell of Cajal and ganglion cells act as pacemakers. These cells help in the process of neurotransmission. Pathological changes in these cells are associated with electrical events and neurotransmission. This is related to hypoperistalsis and voiding dysfunction of MMIHS patients.

Symptoms:

The symptoms associated with this condition are:

• Nausea and vomiting are the most common symptoms in such cases. Bile-stained vomiting is an important clinical sign of this condition. Infants are often unable to pass meconium (a green-colored stool).

• Obstruction of the bowel is one of the most common problems in such cases. This causes abdominal pain, abdominal bloating, and distention of the abdomen. Swelling of the abdomen is a common clinical finding.

• Hypoperistalsis leads to slow passage of the contents and indigestion.

• Patients often suffer from short-bowel syndrome. This causes malabsorption of water, vitamin, minerals, protein, and fat.

• The colon is abnormally small.

• Intestinal malrotation causes the twisting and rotation of various parts of the small and large intestines. This causes obstruction in the gastrointestinal tract and ultimately leads to necrosis of the intestine.

• All these intestinal complications cause liver dysfunction, liver failure, and central line infections (infections in the bloodstream).

• Improper closure of the abdominal wall leads to herniation of the abdominal organs in multiple sites.

• Multiple cystic lesions are present in the kidneys. Such cystic lesions show dysplastic (tissue changes that lead to cancerous growth) changes. As a result, the affected kidney becomes known functional. This is known as ureteropelvic atresia.

• Patients often suffer from dilation of the ureter and urinary bladder.

• Retention of urine leads to repeated incidences of urinary tract infections. Vesicoureteral reflux (VUR, backflow of the urine in the urinary tract) is also seen.

• Obstruction in the urinary tract causes repeated infection and inflammation of the kidneys. This causes swelling of the kidneys (hydronephrosis).

• Complete absence of one or both testes can be observed. Testes are seen in the inguinal canal in spite of the scrotum. This is known as Cryptorchism.

• Structural abnormality in the heart and main blood vessels is very common. Tumors in the heart can also be found in some cases.

How to Diagnose Microcolon Intestinal Hypoperistalsis Syndrome?

1. Proper familial history is important. The familial dominant form of this disorder shows family history.

2. A radiograph of the abdomen shows dilated loops of the small vessels and a gasless abdomen.

3. An enlarged urinary bladder is seen in ultrasonography and cystography (imaging analysis of urinary bladder). Also unilateral and bilateral hydronephrosis is also observed.

4. In magnetic resonance imaging, dilated esophagus and micro colon are observed. A micro colon can also be seen in contrast enema.

5. Dilated stomach and small intestine with malnutrition can be found in the fluoroscopic abdomen examination.

6. In histological examination, vacuolar degeneration and proliferation of the connective tissue in the smooth muscle layer are seen.

7. Acetylcholinesterase staining and neural cell adhesion molecule (NCAM) staining demonstrated many ganglioneuromas (rare tumors of automatic nerve cells).

What Are the Treatment Options?

As this is a multisystem disorder, different treatment options are used depending on the severity of the conditions. The treatment options are:

1. Vesicostomy (procedure to make a small incision to drain urine) and clean intermittent catheterizations can be done for decompression of the urinary bladder.

2. Gastrostomy and Jejunostomy are useful for the treatment of removal of obstruction in the small intestine. Bowel diversion procedures like ileostomy and colostomy can be done to eliminate obstruction.

3. Total parenteral nutrition (TPN; supplementation of daily nutrients) is for maintaining nutritional values and intestinal dysmotility.

Conclusion:

Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a multisystem genetic disorder. Obstruction of the colon, malabsorption of food, and urinary tract complications are common symptoms of this condition. Abnormality of the smooth muscle is associated with this. Surgical corrections are the mood of treatment in such cases.