Hydronephrosis and Hydroureter Treatment & Management

In fetuses with severe oligohydramnios and documented lung maturation, early delivery has been suggested. Although no data document improved renal outcome with early delivery, early delivery may be indicated to reduce the risk of other adverse outcomes from oligohydramnios, such as umbilical cord compression.

The role of medical treatment of hydronephrosis and hydroureter in adults is limited to pain control and treatment or prevention of infection. Most conditions require either minimally invasive or open surgical treatment. Two notable exceptions are (1) oral alkalinization therapy for uric acid stones and (2) steroid therapy for retroperitoneal fibrosis.

The management approach to infants with antenatal hydronephrosis is based on the confirmation of persistent postnatal hydronephrosis and the following two predictive factors:

• Bilateral involvement
• Severe hydronephrosis: Fetuses with a renal pelvic diameter greater than 15 mm during the third trimester are at the greatest risk for significant kidney disease

Bilateral hydronephrosis

Infants with severe bilateral antenatal hydronephrosis and/or bladder distension are at increased likelihood of having significant disease. These infants and those with a severe hydronephrotic solitary kidney should be evaluated initially by ultrasonography on the first postnatal day. Bilateral hydronephrosis suggests an obstructive process at the level of or distal to the bladder, such as ureterocele or posterior urethral valves (PUV) in a male infant, which can be associated with impaired renal function and ongoing renal injury.

If postnatal ultrasonography demonstrates persistent hydronephrosis, voiding cystourethrography (VCUG) should be performed. In male infants, the posterior urethra should be fully evaluated to detect possible PUVs.

Infants with mild or moderate hydronephrosis can be evaluated after 7 days of life.

Severe unilateral hydronephrosis

In newborns with severe antenatal unilateral hydronephrosis (renal pelvic diameter > 15 mm in the third trimester), ultrasonography should be performed after the infant returns to birth weight (after age 48 h and within the first 2 wk of life).

Moderate and mild unilateral hydronephrosis

In newborns with less severe antenatal unilateral hydronephrosis (renal pelvic diameter < 15 mm during third trimester), ultrasonography can be performed after age 7 days to see whether the hydronephrosis has persisted postnatally.

Moderate hydronephrosis resolves by age 18 months in most cases. This was illustrated by a prospective study of 282 infants (age 2 mo) with renal pelvic diameters between 10 and 15 mm, which resolved in 94% of patients by age 12-14 months (resolution was defined as renal pelvic diameter ≤5 mm on two consecutive ultrasounds). Of the 18 patients with persistent hydronephrosis, 14 had ureteropelvic junction (UPJ) obstruction and 4 had vesicoureteral reflux (VUR). ^[31]

Antibiotic prophylaxis

Higher rates of urinary tract infection (UTI) have been reported in children with prenatally diagnosed hydronephrosis compared with the general pediatric population. ^{[32, 33]} The risk of infection rises if there is an underlying urologic abnormality, such as VUR or obstructive uropathy, and is greater in girls than in boys. ^[34]

As a result, in infants with severe hydronephrosis who are at greater risk for an underlying urologic abnormality, antibiotic prophylaxis is started after delivery until the diagnosis of VUR or obstructive uropathy is excluded.

Antibiotic prophylaxis in children with mild or moderate hydronephrosis confirmed postnatally has not been studied prospectively. However, a prospective study of 237 children diagnosed with prenatal hydronephrosis found that those with ureteral diameter 7 mm or greater had three times the risk of UTI regardless of the presence of VUR and would likely benefit from continuous antibiotic prophylaxis. Conversely, patients with non-refluxing hydroureter less than 7 mm were not at increased risk of UTI. ^[35]  

In one retrospective study of 1514 with mild persistent hydronephrosis, the use of prophylactic antibiotics reduced the risk of febrile UTI in patients who had VUR. ^[36] Until further prospective studies are conducted, antibiotic prophylaxis should be considered until VCUG has been performed and either the diagnosis of VUR has been made or eliminated.

Antibiotic prophylaxis is not needed in infants with normal postnatal ultrasonography findings. ^[37]

Four retrospective studies have considered the role of antibiotic prophylaxis in infants with hydronephrosis. Zareba et al analyzed the risk factors for UTI in 376 infants with prenatal hydronephrosis and reported that infants with high-grade hydronephrosis, girls, and uncircumcised boys were at highest risk for UTI. Antibiotic prophylaxis did not decrease the risk in any of the groups studied. ^[38]

In a systematic review that included 3876 newborns with antenatal hydronephrosis, Braga et al found that infants with high-grade hydronephrosis receiving continuous antibiotic prophylaxis (CAP) had significantly lower UTI rates than those who did not receive an antibiotic regimen (14.6% vs 28.9%). However, the rates for infants with low-grade hydronephrosis were similar (2.2% vs. 2.8%). The researchers cautioned that the level of evidence of available data was moderate to low. ^[39]

Herz et al reviewed the records of 278 children maintained on CAP and 127 who were not and compared individual characteristics to determine risk factors for UTI. The presence of ureteral dilation, high-grade VUR, and ureterovesical junction obstruction were independent risk factors for development of UTI. CAP had a significant role in reducing UTI in children with the risk factors but was unnecessary otherwise. ^[40]

Varda et al studied the use of CAP during the interval between birth and initial neonatal imaging in 494 infants with a history of prenatal urinary tract dilation, and these authors concluded that routine CAP may be of limited benefit in most patients in this setting. The incidence of UTI prior to initial neonatal imaging was low, and was not significantly different in study patients who received CAP and those who did not. The ropensity score adjusted odds of developing UTI with CAP versus without was 0.93 (95% CI 0.10-8.32; P = 0.95). ^[41]

A systematic review from the European Association of Urology/European Society for Paediatric Urology Guidelines Panel found that most studies of CAP had low-to-moderate quality of evidence and high risk of bias. Consequently, the panel concluded that whether CAP is superior to observation in decreasing UTIs remains unproven. However, CAP may be warranted in uncircumcised boys, children with ureteral dilatation, and those with high-grade hydronephrosis, who may be more likely to develop UTI. ^[42]

The specific treatment of a patient with hydronephrosis and hydroureter depends, of course, on the etiology of the process. Several factors help determine the urgency with which treatment should be initiated. In general, any signs of infection within the obstructed system warrant urgent intervention because infection with hydronephrosis may progress rapidly to sepsis. A mildly elevated white blood cell count is often observed in patients with stones but does not necessarily mandate immediate action in the absence of other signs or symptoms of systemic infection. However, even a low-grade fever in a diabetic or immunosuppressed patient (ie, on steroid therapy) requires immediate treatment.

The potential for loss of renal function also adds to the urgency (eg, hydronephrosis or hydroureter bilaterally or in a solitary kidney). Finally, patient symptoms help determine the urgency with which treatment is initiated. For example, refractory pain in a patient with an obstructing ureteral calculus necessitates intervention, as does intractable nausea and vomiting.

Urethral catheterization is important to help rule out a lower tract cause for hydronephrosis and hydroureter. Difficulty in placing a Foley catheter may suggest urethral stricture or bladder neck contracture.

Urologists commonly use ureteral stent placement in cases of intrinsic and extrinsic causes of hydronephrosis. The procedure is usually performed in conjunction with cystoscopy and retrograde pyelography. Stents can bypass an obstruction and dilate the ureter for subsequent endoscopic treatment.

Urologists or interventional radiologists can place a percutaneous nephrostomy tube if ureteral stenting is not possible. Usually, ultrasonography is used first to locate the dilated collecting system. Using the Seldinger technique, a tube ranging from 8-12F can be placed. Nephrostomies are typically placed when a retrograde stent cannot be passed because of anatomic changes in the bladder or high-grade obstruction in the ureter. Because this procedure can be performed under local anesthesia, patients who are too hemodynamically unstable for general anesthesia may undergo percutaneous nephrostomy tube placement. In addition, nephrostomy tube placement may be performed with minimal use of radiation and may be useful in pregnant patients.

In a study of fluoroscopically guided percutaneous nephrostomy (PCN) placement in infants and young children (mean age 8.6 months; range, 1 day-75.5 mo), Hwang et al reported achieving complete decompression of hydronephrosis in 35 of 53 kidneys (66%) and incomplete decompression in 17 of 55 kidneys (32.1%). The authors concluded that PCN is a feasible and effective option for relieving urinary obstruction in these patients, and can serve as a bridging procedure to definitive corrective surgery. ^[43]

Advances in endoscopic and percutaneous instrumentation have decreased the role of open or laparoscopic surgery for hydronephrosis. Certain causes of hydronephrosis, mostly extrinsic, still require treatment with open surgery. Examples include retroperitoneal fibrosis, retroperitoneal tumors, and aortic aneurysms. Some stones that cannot be treated endoscopically or with extracorporeal shockwave lithotripsy require open removal. Although endoscopic management does play a role in low-grade low-stage ureteral tumors, these lesions also usually require open or laparoscopic surgical management.

Urine should be collected from the kidney when obstruction is relieved to allow identification and targeted treatment of any infection that may be present.

Fetal surgery

Although several prospective and retrospective studies have examined antenatal surgery in fetuses with sonographic findings consistent with lower urinary tract obstruction, no good evidence supports that this intervention improves renal outcome. ^[44] Although these procedures may increase the amount of amniotic fluid, thus potentially improving lung development and survival rate, the rate of chronic renal disease is high in survivors, necessitating renal replacement therapy in almost two thirds of the cases.

The benefit of vesicoamniotic shunting (VAS) proved inconclusive in the Percutaneous vesicoamniotic shunting in Lower Urinary Tract Obstruction (PLUTO) trial, which compared VAS with conservative nonsurgical management in 31 singleton fetuses younger than 28 weeks’ gestation with isolated bladder outflow obstruction. Although survival to 28 days and 1 year appeared to be higher with VAS than with conservative management, the PLUTO investigators could not prove benefit beyond reasonable doubt, and VAS was substantially more costly. ^[45]

Newborns in the PLUTO trial had a very low chance of surviving with normal renal function, regardless of whether they underwent VAS. Short-term and long-term morbidity in both trial groups was substantial, and complications of VAS resulted in pregnancy loss in some cases. ^[45]

Refer the patient to a urologist whenever hydronephrosis or hydroureter is newly diagnosed. Further consultations may be sought by the urologist, depending on the circumstances. For example, a nephrologist's input would be useful in cases of severe pathological postobstructive diuresis. In addition, an interventional radiologist would be needed for nephrostomy tube placement if urgent decompression is needed and ureteral stent placement is not possible. Patients with antenatal and postnatal hydronephrosis should be referred to a pediatric urologist for evaluation and management.

Monitor patients for postobstructive diuresis. This is a marked polyuria observed after relief of an obstructed system.

Patients who are most likely to experience postobstructive diuresis present with chronic obstruction, edema, congestive heart failure, hypertension, weight gain, and azotemia. Clinically significant postobstructive diuresis is usually seen only in the setting of prior bilateral obstruction or, similarly, a unilateral obstruction of a solitary functioning kidney.

This postobstructive diureses can lead to a marked diuresis with the wasting of sodium, potassium, phosphate, and the divalent cations. Management involves avoiding severe volume depletion, hypokalemia, hyponatremia, hypernatremia, and hypomagnesemia.

Volume or free-water replacement is appropriate only when the salt and water losses result in volume depletion or a disturbance of osmolality. In many cases, excessive volume or fluid replacement prolongs the diuresis and natriuresis. An appropriate starting fluid for replacement is 0.45% saline. During this period, vital signs, volume status, urine output, and serum and urine chemistry and osmolality should be monitored.

Postobstructive diuresis is usually self-limited. It usually lasts for several days to a week but may, in rare cases, persist for months.

Once the diagnosis is made and treatment is performed, follow-up imaging studies are necessary to assess for resolution of the hydronephrosis and hydroureter. Additionally, laboratory studies of renal function should be performed, to assess the recovery of renal function.

For ultrasonography follow-up, fetuses with mild hydronephrosis should have follow-up ultrasonography in the third trimester (32-34 wk gestation). The interval for follow-up examination and management is dictated by the initial findings and the amount of amniotic fluid. Those with resolution have a low risk of clinically significant pathology and do not need further antenatal or postnatal evaluation. Serial follow-up ultrasonography is indicated for fetuses with the following:

• Moderate or severe hydronephrosis

• Bilateral involvement

• Progression and/or persistence of hydronephrosis

• Normal amniotic fluid volume: Fetuses with unilateral involvement and normal amniotic fluid volume should have repeat prenatal ultrasonography examination at 32-34 weeks of gestation to evaluate and guide postnatal evaluation.

• Bilateral hydronephrosis and normal amniotic fluid volume: These patients should have repeat ultrasonography examination 2-3 weeks after diagnosis to evaluate for progression and amniotic fluid volume. Follow-up examinations are determined according to the serial ultrasonography results.

For follow-up in older children with hydronephrosis, most protocols recommend serial monitoring with ultrasound and diuretic renography. Indications for surgery include worsening of hydronephrosis, lithiasis, recurrent infections, or deterioration of renal function. Although diuretic renography remains the gold standard for the diagnosis of obstructive hydronephrosis, the use of color Doppler ultrasound to determine hydronephrosis grading and the absence of ureteral jets offers an accurate and noninvasive option that can limit the need for renography. ^[46]