Horseshoe kidney overview

# Overview
Horseshoe kidney is the congenital disorder of kidneys in which the isthmus of both kidneys fuse together during embryonic development leading to appearance of "Horseshoe". It is the most common fusion defect of kidneys.

# Historical Perspective
Before 1800 A.D. horseshoe kidney regarded as curiosity found only at postmortem examination.However with the advent of the roentgen rays and the intravenous pyelography the diagnostic possibilities to recognize the horseshoe kidney improved, which was later on aided by the ultrasound and computed tomography scan by which horseshoe kidney can be easily diagnosed.

# Classification
Horseshoe kidney may be classified into three groups based on:
- morphological appearance of fusion,
- Site of the fusion,
- Vascular supply or angiographic appearance of the vessels.

# Pathophysiology
Most people with horseshoe kidneys are totally asymptomatic and their kidneys function normally throughout their lives. About quarter of cases are found incidentally, usually during a CT scan due to some other problem. Nonetheless, there are lots of other patients who are predisposed to certain medical sequelae due to the embrogenesis or intrinsic anatomical abnormalities.

# Causes
During early fetal development, the kidneys are developed in the pelvis and then later they move upwards in abdomen. Sometimes due to unknown reason the lower ends of both kidneys fuse together forming a 'U' shaped single kidney.

# Differentiating Horseshoe kidney from Other Diseases
Horseshoe kidney disease must be differentiated from Renal ectopia, Ureteropelvic junction obstruction, Hydronephrosis and Duplicate collecting systems that can be differentiated based on appearances on CT scan.

# Epidemiology and Demographics
- Horseshoe kidney is a fairly common condition among other renal fusion abnormalities.Males cases are twice more common than female cases.Although it has been seen in members of same families, but no any particular gene has been found to cause this disease.

# Risk Factors and Associations
There are no particular gene discovered yet which are directly related to horseshoe kidney but it has been seen associated with other genetic disorders such as Turner syndrome and Edwards syndrome, further suggesting that it is linked to some genes.

# Screening
There is no particular screening test for horseshoe kidney itself, although CT scanning or renal ultrasonography can be used to screen for the presence of stones, masses, or hydronephrosis.

# Natural History, Complications, and Prognosis
The majority of patients with horseshoe kidney are asymptomatic and incidentally detected during renal imaging.However the outcome depends on associated urological problems.

# Diagnosis

## Diagnostic Study of Choice
Intravenous pyelography is considered the best initial test.

## History and Symptoms
The majority of patients with horseshoe kidney are asymptomatic.The most common symptoms of horseshoe kidney include abdominal or flank pain,abdominal mass,hematuria and pyuria.

## Physical Examination
Patients with horseshoe kidney usually appear well and in majority of cases horseshoe kidney is an incidental finding during radiological examination. Physical examination of patients with horseshoe kidney is usually remarkable for  abdominal distension, palpable kidney, costovertebral tenderness and palpable bladder.

## Laboratory Findings
Urine routine (DR) and urine culture should be done to look for any sign of urinary infection and serum creatinine and electrolytes should be done to check the kidney function.

## X-ray
There are no x-ray findings associated with horseshoe kidney,other than lower renal outline than normal kidneys. However, an x-ray may be helpful in the diagnosis of complications of horseshoe kidney, which include hydronephrosis due to obstruction and renal stones.

## Ultrasound
Ultrasound may be helpful in the diagnosis of horseshoe kidney.Findings on an ultrasound diagnostic of horseshoe kidney include soft tissue mass,curved configuration or elongation of the lower poles and poorly defined lower poles and lower positioning of upper pole of kidney in abdomen.

## CT scan
CT Scan with contrast is imaging technique of choice. CT Scan of abdomen and pelvis with and without contract is used to look for location of kidneys. It is accurate in determining the anatomical location and also help in differentiating the parenchymal from fibrous isthmus.

## MRI
MRI is also helpful in diagnosing horseshoe kidney, and is used in conditions where CT Scan is not recommended or available. MRI is also costlier than CT Scan.

## Other Imaging Findings
Other imaging studies such as Renal scintigraphy, also known as "renal scans", can also be used in the diagnosis of horseshoe kidney, by accessing its anatomical structure,renal function and drainage.

# Treatment
There is no treatment required for horseshoe if asymptomatic.The mainstay of therapy is supportive and symptomatic care depending upon the symptoms.

## Medical Therapy
Pharmacologic medical therapy is recommended among patients with Urinary tract infection.

## Interventions
Horseshoe kidney is considered to be asymptomatic and non-fatal renal anomaly that has excellent prognosis in majority of patients without any therapeutic intervention.However in some of the patient medical as well as surgical management required based on the clinical course of the disease.

## Surgery
Although most of the patients doesn't require surgical intervention but it depends upon the disease process itself and its complications.

## Primary Prevention
There are no established measures for the primary prevention of horseshoe kidney disease.

## Secondary Prevention
There are no established measures for the secondary prevention of horseshoe kidney disease.