OVERVIEW

What is the normal process of urine excretion?

The urinary system consists of four parts from top to bottom: kidneys, ureters, bladder, and urethra (the first two are collectively called the upper urinary tract, and the latter two are called the lower urinary tract). Blood undergoes filtration and reabsorption in the renal parenchyma to form urine.

Urine gradually drains from the renal pelvis into the ureters and bladder, and is eventually expelled from the body through the urethra.

What is the relationship between the kidney and the renal pelvis?

Urine produced by the kidneys flows into the funnel-shaped minor calyces (approximately 7–8 per kidney), then into the major calyces formed by the convergence of 2–3 minor calyces (about 2–3 per kidney), and finally into the renal pelvis (normally only one per kidney), which is formed by the merging of the major calyces.

The renal pelvis functions as a collection site for urine within the kidney, acting like a central hub for the kidney's drainage system.

What is obstructive nephropathy?

Obstructive nephropathy refers to a condition where urine outflow from the kidneys is obstructed due to various causes, leading to structural and functional damage to the kidneys.

Does obstructive nephropathy always affect only one kidney?

Obstructive nephropathy primarily occurs unilaterally, with no definitive statistics on left vs. right incidence due to varying causes, but it can also occur bilaterally. The condition may present acutely (sudden onset) or chronically (gradual progression).

It can manifest as either complete or partial obstruction. Therefore, the severity of the condition depends on factors such as the degree and nature of the obstruction.

SYMPTOMS

What are the specific clinical manifestations of obstructive nephropathy?

The disease has various causes, and symptoms can be divided into those caused by the primary disease and those related to the kidneys. Common kidney-related symptoms include:

• Lumbar discomfort: In cases such as acute ureteral obstruction due to stones, it may present as paroxysmal colicky pain on the affected side of the lower back, which can be severe enough to cause restlessness and an inability to sit still. The pain may also radiate to the abdomen on the affected side, or even to the penis or scrotum.
  In chronic cases, it often manifests as a dull, uncomfortable ache on the affected side of the lower back, which may progressively worsen.

• Urinary dysfunction: Mainly refers to abnormal urine output. In cases of acute complete bilateral obstruction or chronic progressive bilateral kidney damage, it may present as anuria (no urine output). Most patients experience partial obstruction, often showing reduced urine output or even anuria during episodes, followed by increased urine output during remission.

• Hypertension: Quite common. If the obstruction is relieved early, blood pressure usually improves. However, if the condition persists for a long time, hypertension may continue even after the obstruction is relieved, sometimes without improvement.

• Polycythemia: Often detected through routine blood tests, showing red blood cell counts higher than the upper limit of normal. This is thought to be related to increased erythropoietin production due to long-term stimulation.

• Acidosis: Simply put, it refers to the kidneys' impaired ability to excrete acidic substances, leading to an accumulation of acid in the body.

CAUSES

What are the causes of obstructive nephropathy?

The causes of this disease are numerous and can be broadly divided into two categories: genitourinary system-related causes and non-genitourinary causes such as gynecological or intestinal diseases. These include:

• The genitourinary system, from top to bottom, can be roughly categorized as follows:

• Kidney diseases: such as renal pelvis stones, renal pelvis tumors, congenital abnormalities of the ureteropelvic junction, etc.;

• Ureteral diseases: such as ureteral stones, ureteral tumors, ureteral strictures, accidental ligation during surgery, etc.;

• Bladder diseases: such as bladder stones, bladder tumors, ureteroceles, neurogenic bladder, etc.;

• Urethral diseases: such as urethral stones, urethral foreign bodies, urethral strictures, etc.;

• Reproductive system diseases: such as prostate cancer, benign prostatic hyperplasia, etc.;

• Non-genitourinary causes, such as gynecological or intestinal diseases: conditions in surrounding organs that can lead to urinary tract obstruction, such as cervical cancer invading the ureter, intestinal tumors compressing the ureter, or retroperitoneal conditions like inflammation or tumors.

With so many causes of obstructive nephropathy, what are the most common ones?

The disease has complex and diverse causes, which vary with age and gender. In children, congenital conditions are most common, such as ureteropelvic junction obstruction. In young adults, urinary tract stones are frequent. In the elderly, benign prostatic hyperplasia and tumors are the most prevalent causes.

DIAGNOSIS

What tests are needed for the diagnosis of obstructive nephropathy and their significance?

In fact, each test has its own advantages and disadvantages, so multiple tests are often required to further clarify the condition for each disease.

• Renal function + electrolytes: A blood test primarily examining creatinine, blood urea nitrogen, serum cystatin C, and electrolytes such as potassium levels to assess the degree of kidney damage.

• Complete blood count (CBC): A blood test mainly observing changes in white blood cells, red blood cells, etc.

• Urinalysis: Determines the presence of white blood cells, red blood cells, proteinuria, and urine pH. Most cases show proteinuria, though usually in small amounts.

• Urinary tract ultrasound: A simple, convenient, non-invasive test that can be performed bedside but is susceptible to intestinal gas interference and operator experience. It helps evaluate kidney size, morphology, the severity of hydronephrosis, and may assist in identifying the cause of obstruction.

• Abdominal X-ray: Low radiation and inexpensive, but affected by intestinal gas. It assesses kidney contour and size and can detect radiopaque stones, though often serves only as a preliminary test due to limited clarity.

• Non-contrast CT scan: Involves radiation exposure and is relatively costly. It provides detailed information on kidney size, morphology, hydronephrosis, and may help identify causes of obstruction, such as urinary stones, intestinal masses, or retroperitoneal lesions.

• Others: Due to the diverse and complex causes of this condition, additional tests like KUB+IVP, contrast-enhanced CT, colonoscopy, hysteroscopy, or cystoscopy may be required.

TREATMENT

Which department should be consulted for obstructive nephropathy?

Usually consult the urology or nephrology department.

How should obstructive nephropathy be treated?

The treatment aims to relieve obstruction and restore kidney function.

• In cases of bilateral acute complete obstruction, emergency measures to ensure urine drainage are often required, such as retrograde urinary catheterization, nephrostomy, or catheterization. Further treatment is scheduled once the condition stabilizes.

• If the condition permits, diagnostic tests should first be completed to identify the cause of obstruction. Further treatment is then determined based on the underlying cause, such as ureteroscopic lithotripsy or laparoscopic stone removal for ureteral stones, or transurethral resection of the prostate for benign prostatic hyperplasia.

DIET & LIFESTYLE

What should patients with obstructive nephropathy pay attention to in daily life?

• Get timely examinations to identify the cause and severity of the disease;

• Seek prompt treatment and adopt the best treatment method based on the cause;

• Depending on the cause, attention should be paid to lifestyle, diet, and other aspects.

• After treatment, regular follow-up examinations are still necessary.

PREVENTION

How to prevent obstructive nephropathy?

Identify the cause promptly and actively treat the primary disease.