eMedicine Specialties > Urology > Hydronephrosis and Ureter Disorders

Hydronephrosis and Hydroureter

Author: Srinivas Vourganti, MD, Staff Physician, Department of Urology, Case Western Reserve University, University Hospitals of Cleveland
Coauthor(s): Prakash Maniam, MD, Staff Physician, Department of Urology, St Mary's Hospital of Troy
Contributor Information and Disclosures

Updated: Feb 25, 2008

Introduction

Background

Hydronephrosis and hydroureter are common clinical conditions encountered not only by urologists but also by emergency medicine specialists and primary care physicians. Hydronephrosis is defined as a dilation of the renal pelvis and calyces. Analogously, hydroureter is defined as a dilation of the ureter. The presence of hydronephrosis or hydroureter should be considered a physiologic response to the interruption of the flow of urine. Although this is often due to an obstructive process, in some cases, such as megaureter secondary to prenatal reflux, the collecting system may be dilated in the absence of obstruction. In addition, obstruction can sometimes occur in the absence of a dilated urinary tract. Thus, the terms hydronephrosis and obstruction should not be used interchangeably.

Hydronephrosis and hydroureter can range from benign processes, such as the physiologic hydroureteronephrosis of pregnancy, to potential life-threatening situations, such as infected hydronephrosis or pyonephrosis. Although patients usually present with some signs or symptoms, hydronephrosis can be an incidental finding encountered during the evaluation of an unrelated process. If unrecognized or left untreated, hydronephrosis and hydroureter secondary to obstruction can lead to hypertension, loss of renal function, and sepsis. Consequently, all patients found to have hydronephrosis or hydroureter should undergo a thorough evaluation and should be referred to a urologist.

Pathophysiology

Hydronephrosis can result from anatomic or functional processes interrupting the flow of urine. This interruption can occur anywhere along the urinary tract from the kidneys to the urethral meatus. The rise in ureteral pressure leads to marked changes in glomerular filtration, tubular function, and renal blood flow. The glomerular filtration rate (GFR) declines significantly within hours following acute obstruction. This significant decline of GFR can persist for weeks after relief of obstruction. In addition, renal tubular ability to transport sodium, potassium, and protons and concentrate and to dilute the urine is severely impaired. The extent and persistence of these functional insults is directly related to the duration and extent of the obstruction. Brief disruptions are limited to reversible functional disturbance with little associated anatomic changes. More chronic disruptions lead to profound tubular atrophy and permanent nephron loss.

Increased ureteral pressure also results in pyelovenous and pyelolymphatic backflow. Gross changes within the urinary tract similarly depend on the duration, degree, and level of obstruction. Within the intrarenal collecting system, the degree of dilation is limited by surrounding renal parenchyma. However, the extrarenal components can dilate to the point of tortuosity.

To distinguish acute and chronic hydronephrosis, one may consider acute as hydronephrosis that, when corrected, allows full recovery of renal function. Conversely, chronic hydronephrosis is a situation in which the loss of function is irreversible even with correction of the obstruction. Early experiments with dogs showed that if acute unilateral obstruction is corrected within 2 weeks, full recovery of renal function is possible. However, after 6 weeks of obstruction, function is irreversibly lost.

Grossly, an acutely hydronephrotic system can be associated with little anatomic disturbance to renal parenchyma. On the other hand, a chronically dilated system may be associated with compression of the papillae, thinning of the parenchyma around the calyces, and coalescence of the septa between calyces. Eventually, cortical atrophy progresses to the point at which only a thin rim of parenchyma is present. Microscopic changes consist of dilation of the tubular lumen and flattening of the tubular epithelium. Fibrotic changes and increased collagen deposition are observed in the peritubular interstitium.

Frequency

United States

The frequency of hydronephrosis in a large autopsy series, ranging from birth to age 80 years, was 3.1%. The prevalence rate was 2.9% in females and 3.3% in males.

Mortality/Morbidity

• Long-standing hydronephrosis may be associated with obstructive nephropathy and renal failure.
• Urinary stasis may result in infection, renal scarring, calculus formation, and sepsis.
• Renovascular hypertension may result from renin secretion from the hydronephrotic kidney. The incidence rate of hypertension after acute unilateral obstruction has been reported to be 20-30%. In patients with unilateral obstruction and hypertension, the hypertension can be reversed with treatment of the obstruction. Reversal of the hypertension is most likely to occur if an increase in renin production is measured in the hydronephrotic kidney along with a decrease in renin secretion from the contralateral kidney. Also, these patients demonstrate ACE-inhibitor–responsive hypertension. Therefore, if lateralizing renin secretion can be demonstrated, then the obstruction should be treated to normalize blood pressure.

Sex

• In women, gynecologic cancers and pregnancy are common causes. As such, among younger patients (aged 20-60 y), the frequency of hydronephrosis is higher in women than in men.
• In men, obstruction secondary to prostatic hypertrophy and prostate cancer are the major causes of hydronephrosis. Consequently, among older patients (>60 y), the frequency of hydronephrosis is higher in men than in women.

Age

• In young adults, calculi are the most common causes of hydroureter and hydronephrosis.
• In children, reflux and ureteropelvic junction obstruction are common causes.

Clinical

History

• Symptoms vary depending on whether the hydronephrosis is acute or chronic.
• With acute obstruction, patients may present with pain, which is usually described as severe, intermittent, and dull. Patients may describe worsening of pain with consumption of fluids. Depending on the level of hydroureter, pain may radiate to the ipsilateral testicle or labia. Often associated with nausea and vomiting, pain from an obstructed system is referred to as renal colic.
• A history of hematuria may herald a stone or malignancy anywhere in the urinary tract.
• A history of fever or diabetes adds urgency to the evaluation and treatment.
• A history of a solitary kidney is an emergent situation.
• Hydronephrosis may develop silently, without symptoms, as the result of advanced pelvic malignancy or severe urinary retention from bladder outlet obstruction.
• Bilateral symmetrical hydronephrosis usually suggests a cause related to the bladder, such as retention, prostatic blockage, or severe bladder prolapse.¹

Physical

• With severe hydronephrosis, the kidney may be palpable.
• With bilateral hydronephrosis, lower extremity edema may occur. Costovertebral angle tenderness on the affected side is common.
• A palpably distended bladder adds evidence of lower urinary tract obstruction.
• A digital rectal examination should be performed to assess sphincter tone and to look for hypertrophy, nodules, or induration of the prostate.

Causes

A multitude of causes exist for hydronephrosis and hydroureter. Classification can be made according to the level within the urinary tract and whether the etiology is intrinsic, extrinsic, or functional.

• Ureter
  • Intrinsic
    • Ureteropelvic junction stricture
    • Ureterovesical junction obstruction
    • Papillary necrosis
    • Ureteral folds
    • Ureteral valves
    • Ureteral stricture (iatrogenic)
    • Blood clot
    • Benign fibroepithelial polyps
    • Ureteral tumor
    • Fungus ball
    • Ureteral calculus
    • Ureterocele
    • Endometriosis
    • Tuberculosis
    • Retrocaval ureter
  • Functional
    • Gram-negative infection
    • Neurogenic bladder
  • Extrinsic
    • Retroperitoneal lymphoma
    • Retroperitoneal sarcoma
    • Cervical cancer
    • Prostate cancer
    • Retroperitoneal fibrosis
    • Aortic aneurysm
    • Inflammatory bowel disease
    • Ovarian vein syndrome
    • Retrocaval ureter
    • Uterine prolapse
    • Pregnancy
    • Iatrogenic ureteral ligation
    • Ovarian cysts
    • Diverticulitis
    • Tuboovarian abscess
    • Retroperitoneal hemorrhage
    • Lymphocele
• Bladder
  • Intrinsic
    • Bladder carcinoma
    • Bladder calculi
    • Bladder neck contracture
    • Cystocele
    • Primary bladder neck hypertrophy
    • Bladder diverticula
  • Functional
    • Neurogenic bladder
    • Vesicoureteral reflux
  • Extrinsic - Pelvic lipomatosis
• Urethra
  • Intrinsic
    • Urethral stricture
    • Urethral valves
    • Urethral diverticula
    • Urethral atresia
    • Labial fusion
  • Extrinsic - Benign prostatic hyperplasia and prostate cancer

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