Diseases & Conditions
Hydronephrosis
Authors: Byron D. Joyner, MD
Last updated: April 18, 2006
- Overview |
- Symptoms |
- Causes |
- Diagnosis |
- Treatment
- Self-care |
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Overview
The kidneys are located in the back of the abdomen underneath the liver on the right and the spleen on the left. These important organs are protected by the ribs on all sides. The kidneys have many functions, the most important of which is to filter the blood of waste products thereby making urine. Once urine is made, it passes into the bladder by way of tubes called ureters. Once the bladder is full, urine is eliminated through a tube called the urethra.
Symptoms
Children with Ureteropelvic Junction (UPJ) obstruction present with variable symptoms, such as episodic flank -or abdominal pain and urinary tract infections. Cyclical abdominal pain, often associated with vomiting, is a typical presentation.
Stone disease may be associated with UPJ obstruction; in fact, the incidence of kidney stone disease is 17 times higher in patients with UPJ obstruction compared to normal populations.
Hematuria is another manner in which UPJ obstruction may present. Following trivial trauma, friable mucosal vessels in the dilated collecting system presumably rupture. Some children with UPJ obstruction have insidious presentations with years of relative anorexia associated with difficulty gaining weight. These children are typically found to have a left UPJ obstruction. The dilated left renal pelvis creates a mass effect on the stomach, which may result in early satiety, relative anorexia and vomiting. Still, other children with UPJ obstruction may present with profound urosepsis.
Causes
The development of the kidney is very complex. Sometimes during development, certain conditions may occur that change the way the kidneys look and function. One such condition is called hydronephrosis. This condition results in stretching of the collecting system of the kidney, called the renal pelvis. A major cause of hydronephrosis occurs when the urine cannot move to the bladder because the flow of urine is obstructed. Such conditions that create this problem occur at the level of the kidney where the ureter meets the renal pelvis (ureteropelvic junction obstruction) or where the ureter meets the bladder (ureterovesical junction obstruction). Another major cause of hydronephrosis is vesicoureteral reflux. This condition results in the backflow of urine from the bladder to one or both of the kidneys.
Hydronephrosis is the most common problem detected on prenatal ultrasound, effecting approximately 1% to 5% of all pregnancies. Hydronephrosis is so frequently encountered in prenatal ultrasounds, in fact, that in 1988 doctors developed a universal language especially for kidneys affected by this problem. This language, developed initially to describe prenatal kidneys, includes 4 different grades of hydronephrosis. Grade I – IV, with IV being the worst type of hydronephrosis. Since the early 1990’s, this grading system has been adapted to describe hydronephrosis for all ages.
Ureteropelvic junction (UPJ) obstruction is the most common of the types of problems causing hydronephrosis, with an incidence of 1 in 1250 live births. UPJ obstruction is twice as common in boys as in girls. Most of these occur on the left side. Both kidneys are affected in a 25% of cases. Most cases of hydronephrosis are found during the prenatal screening with only 19% of children presenting with clinical manifestations of abdominal mass, blood in the urine, vomiting, feeding difficulties and urinary tract infections. Ever since prenatal ultrasounds were endorsed by the American Institute for Ultrasound in Medicine Bioeffects Committee, maternal-fetal ultrasounds have been performed as a protocol during pregnancy to discover any antenatal problems.
Diagnosis & Related Conditions
Although UPJ obstruction is the most common cause of hydronephrosis, there are many other disease entities that may manifest as hydronephrosis. One way to develop this list –or differential diagnosis is to think of those disease processes that may create swelling of the renal pelvis. One method of doing this is to develop categories of hydronephrosis: for example, obstructive and non-obstructive (Table 1).
Table 1: Differential Diagnosis of Hydronephrosis
| Obstructive | Non-obstructive |
|---|---|
| Ureteropelvic Junction Obstruction (UPJ) | Vesicoureteral Reflux (VUR) |
| Ureterovesical Junction Obstruction (UVJ) | Physiologic Dilation |
| Multicystic Dysplastic Kidney (MCDK) | Prune Belly Syndrome (PBS) |
| Ureterocele | Renal Cystic Diseases (RCD) |
| Duplicated Collecting System | Megacalycosis |
| Posterior Urethral Valves (PUV) | |
| Ectopic Ureter | |
| Urethral Artesia | |
| Sacrococcygeal Teratoma | |
| Hydrometrocolpos |
There is a large arsenal of radiographic studies available for this purpose. The sequence and timing of these studies is determined largely protocol. The most common study performed is the renal ultrasound. It is a widely available, inexpensive, non-invasive, safe test that provides adequate anatomical visualization without radiation exposure. Given these exceptional qualities, it is widely used both in maternal-fetal sonography and for the post-natal infant study. Subsequent studies allow the diagnosis to become more evident. Further radiological tests should be based upon other possible causes of hydronephrosis, as there are a number of conditions that can mimic or produce dilatation of the collecting system with or without urinary tract obstruction.
If the postnatal sonogram confirms characteristic findings consistent with hydronephrosis, the newborn is placed on a prophylactic dose of oral antibiotics (amoxicillin, 15 mg/kg). This regimen has been almost completely eliminated the presentation of urosepsis in infants with the prenatal diagnosis of hydronephrosis. After prophylaxis has been established, a VCUG is performed to rule out vesicoureteral reflux, which can exist even in spite of a negative postnatal renal ultrasound.
Treatment
In most cases, hydronephrosis will resolve spontaneously. In 20 % of the cases, however, hydronephrosis requires surgical intervention. Surgical intervention depends upon
- the diagnosis
- the temporal degree of obstruction and
- the goals of surgery.
The most common form of hydronephrosis requiring surgical intervention is UJP obstruction for which there are several different approaches, at least two major techniques (flap and dismembered) and one goal: preserve renal function by facilitating unobstructed drainage of the renal pelvis.
Self-care
Hydronephrosis is a congenital condition which resolves spontaneously in a majority of cases. As with most congenital conditions, it is best to seek the help of a professional, in this case a pediatric urologist who is fellowship-trained.
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