Urinary tract obstruction in children

Introduction to pediatric urinary tract obstruction Urinary tract obstruction is one of the common causes of renal failure. As long as it is discovered in time, the obstruction is relieved as soon as possible, and most renal failure can be improved. The urinary system is a duct system, and the lumen can be kept clear to maintain the normal function of the urinary system. Obstruction affects the secretion and excretion of urine. Many lesions inside and outside the urinary system can cause luminal obstruction. The location of obstruction may be in the kidney, ureteropelvic junction, ureter itself, ureteropelvic junction, bladder neck or urethra. The closer the obstruction is to the kidney. The faster the hydronephrosis occurs. Urinary obstruction plays an important role in urinary tract diseases in children. Many lesions and obstructions in the urinary system often cause each other, such as infection and stones can cause obstruction. Obstruction of different causes is conducive to the occurrence of infection and stones, which aggravates the complexity of the lesions. Sexual and kidney damage. Therefore, when there is a urinary tract disease, it is necessary to pay attention to the problem of obstruction, and carry out corresponding examinations in order to release the obstruction in time, drain urine and protect kidney function. basic knowledge The proportion of illness: 0.026% Susceptible people: children Mode of infection: non-infectious Complications: urinary incontinence, kidney stones, anemia, hypertension

Causes of urinary tract obstruction in children

(1) Causes of the disease

In terms of the nature of obstruction, the most important is mechanical obstruction, but neurological dysfunction is also an important factor in pediatric urinary tract obstruction. The common causes of urinary tract obstruction in children are briefly described below.

Generally, the obstruction above the ureteral orifice is called upper urinary tract obstruction, and the obstruction of the bladder, bladder neck, posterior urethra and anterior urethra is called lower urinary tract obstruction.

Urethra:

Common causes are stenosis, stenosis can be in the foreskin, urethral or urethra, urethral stricture is caused by trauma or inflammation, and congenital anterior, posterior urethral valve, anterior urethral diverticulum is an important cause of urinary obstruction in children, in addition There are still urethral stones, pelvic and perineal tumors can also cause obstruction.

Bladder and bladder neck:

Bladder neurological dysfunction is a more common cause. In addition, bladder malformations (bladder diverticulum, repeated bladder), stones, intravesical and extracranial tumors often cause obstruction.

ureter:

Stenotic ectopic ureteral orifice, ureteral cyst caused by ureteral obstruction, vesicoureteral reflux is more common in children than in adults, and stone and pelvic tumor infiltration pressure is also the cause of obstruction.

Kidney and kidney pelvis:

The most common is congenital stenosis of the renal pelvis and ureteral junction, but also due to the valve, ectopic vascular compression caused by obstruction, renal malformation (such as the shoe-shaped kidney) and renal ectopic urinary drainage, stones and tumors Can cause obstruction.

(two) pathogenesis

Urinary tract obstruction caused by many lesions inside and outside the urinary system eventually leads to increased intra-renal pressure, renal pelvis and renal pelvis discharge disorder, prolonged residence time in the urinary renal pelvis, dilated renal pelvis, and gradually increased intra-renal pressure. Expansion affects the secretion of urine, while oppressing nearby blood vessels causes anemia atrophy of the renal parenchyma, due to dilated renal pelvis and renal pelvis, renal parenchymal atrophy, renal dysfunction, called hydronephmsis.

Hydronephrosis can be divided into:

1 The renal pelvis enlarges and the renal pelvis wall becomes thinner;

2 Kidney papillary atrophy (the pyelography showed that the cup-shaped renal pelvis gradually flattened and finally protruded to the outer layer);

3 The renal parenchyma is progressively atrophied and thinned. When the renal pelvis is intrarenal, the renal parenchyma atrophy occurs earlier and more severely.

Urinary obstruction, when the urine is blocked from the renal pelvis and renal pelvis, some of the fluid can enter the lymphatic vessels and veins (renal lymphatic reflux, renal pelvic venous reflux), which will slightly reduce the pressure in the renal pelvis and renal tubules, and continue to divide The ability of urinary tract, when the ureter is blocked, uremia often occurs within 3 days. If the obstruction is eliminated within 8 days, the renal function can still be recovered, and the hydronephrosis caused by partial obstruction or intermittent obstruction often reaches the pole. Large volume.

Urinary obstruction due to the location of the obstruction, the nature of the difference is different, kidney, ureteral obstruction (upper urinary tract obstruction), due to the obstruction of the site near the kidney, hydronephrosis develops rapidly, but only the affected side, and the contralateral kidney Often compensatory hypertrophy, so the total renal function is normal, when the bladder below the obstruction, due to bladder muscle thickening, strengthen the urination force to overcome obstruction, bladder muscle bundle inconsistency, such as long duration, the bladder mucosa convex from the muscle bundle Out, the formation of trabecular pseudo-diverticulum, due to bladder compretion, the bladder neck, triangular tissue hypertrophy, bulging, if the inflammation is more serious bladder neck obstruction, when the enhanced urinary strength can not be overcome When obstructing, there is residual urine after each urination. Generally speaking, the amount of residual urine is directly proportional to the degree of bladder function deficiency. Following the kidney, ureteral water, ureteral wall muscle thickening, ureteral expansion and elongation, forming a tortuous, Adhesion, fixation, aggravation of obstruction and hydronephrosis, urinary obstruction below the bladder, although the bladder acts as a buffer area, hydronephrosis develops slowly, bilateral kidney involvement, total Dysfunction, lower urinary tract obstruction The above process.

Pediatric urinary tract obstruction prevention

Must eliminate lower urinary infarction and infection, such as surgery for urethral stricture and other diseases, radical urinary tract infections, especially those that decompose urea, avoid bladder foreign bodies, reduce the occurrence of stones, prevent the occurrence of upper urinary calculi, should eliminate the urinary tract Obstructive factors, such as congenital urinary tract malformation should be actively treated, such as early detection of the foreskin mouth, urethral stricture, timely release, trauma and inflammation should be timely control of inflammation, thorough treatment of urinary tract infections, prevention of urinary tract obstruction .

Pediatric urinary tract obstruction complications Complications, urinary incontinence, kidney stones, anemia, hypertension

Can occur acute, chronic urinary retention or pseudo-urinary incontinence, can be complicated by hydronephrosis, urinary tract infection, kidney stones, kidney function can cause renal insufficiency, manifested as oliguria, even no urine, anemia, high Blood pressure, etc., when the urinary tract infection is serious, it can be complicated with abscess around the urethra. Abscess rupture is easy to form urinary fistula. A large amount of urinary salt is lost. Hypertonic dehydration may occur, high potassium, high chloride acidosis, renal tumor, renal cyst, polycystic Patients with renal or hydronephrosis can be seen with polycythemia, and spontaneous exudation of urine into the abdominal cavity can cause urinary ascites.

Pediatric urinary tract obstruction symptoms Common symptoms oliguric urinary tract infections, loss of appetite, turbidity, turbidity, nausea, urinary pain, urgency, ureteral stricture, hematuria

Due to the location and nature of obstruction and the speed of occurrence, the clinical manifestations are different. If the primary disease causing urinary obstruction is relatively easy to find, such as urinary stones, tumors, etc., there is little clinical manifestation of hydronephrosis. The capacity of pediatric renal pelvis varies with age, from 1 to 1.5 ml around 1 year old, and about 1 ml per year for children under 5 years old, and gradually approaches 5 to 7 ml for adults. Therefore, only when hydronephrosis reaches a serious degree, There may be signs of abdominal mass or renal failure. Another type of hydronephrosis is intermittent hydronephrosis caused by intermittent obstruction. In addition, the initial manifestation of hydronephrosis may be acute urinary tract infection or growth retardation. If you do not notice the obstruction factor, it will delay the correct treatment, urinary tract obstruction in children can be manifested as urinary incontinence, nocturia, etc., urinary tract dysuria caused by lower urinary tract obstruction, frequent urination and urinary incontinence, although there are kidneys and ureters Water accumulation, but no clinical manifestations.

Upper urinary tract obstruction itself has no disease, such as stenosis of the ureteropelvic junction, ectopic vascular compression and other hydronephrosis up to hundreds of milliliters, or even up to 1000 ~ 2000ml, there is abdominal mass, lower urinary tract obstruction For overflow urinary incontinence, and upper urinary tract obstruction, when there is a large amount of urine in the hydronephrosis, there may be urinary incontinence and nocturia. When the urine is stagnant, there may be pain or pain in the waist and abdomen, nausea, vomiting and Reduced urine output, when the obstruction is relieved, the pain disappears, a large amount of urine is discharged, abdominal examination, and sometimes the tumor can be touched. Because of hydronephrosis, there is no conscious or objective symptom. Potential progressive renal disease can cause uremia. Loss of appetite, nausea, vomiting, indigestion and anemia, and may be associated with high blood pressure, urethral stricture and urethritis, can cause chronic epididymitis, urinary tract infection with severe periurethal abscess, abscess rupture to form urinary fistula, Campbeu (1951 828 cases of pediatric hydronephrosis were analyzed, including 512 cases in clinical practice and 15919 cases in 316 cases. See Table 1 for details. It can be seen from Table 1 that most cases are infants and young children, obstructive nephropathy. Due to a variety of causes, clinical manifestations depend on obstruction due to primary disease, obstruction duration, severity and complications, common symptoms suggestive of obstruction case.

1. Lower urinary tract symptoms: urethral stricture, prostatic hypertrophy, neurogenic bladder or bladder tumor invade the bladder neck, often manifested as dysuria, frequent urination, small urine flow, depending on the duration and extent of obstruction, may appear urgent, Chronic urinary retention or pseudo-urinary incontinence.

2. Upper urinary tract symptoms: ureteral stricture, stone movement, typical renal colic and hematuria, when the kidney effusion, can be abdomen and abdominal mass.

3. Impaired renal tubular function: polyuria, nocturia, polydipsia; renal tubular reabsorption, large loss of urinary salt, hyperosmotic dehydration, high potassium and high chloride acidosis.

4. Renal insufficiency: bilateral obstructive lesions cause renal insufficiency, manifested as oliguria, even no urine, loss of appetite, nausea, vomiting and weight loss.

5. Urinary tract infection: In the case of upper urinary tract infection, it is characterized by chills, fever, pain or tenderness of the ribs, urinary burning, urine turbidity, lower urinary tract infection, frequent urination, urgency and dysuria.

6. Kidney stones: It is both the cause of obstruction and the complication of urinary tract obstruction. Most of the stones are guano stone (magnesium ammonium phosphate-calcium carbonate). This is because the urine flow is not smooth and the bacteria are easy to stay and grow. The bacteria of urease decompose urea to produce ammonia, neutralize hydrogen ions in the urine, raise the pH, cause precipitation of magnesium ammonium phosphate-calcium carbonate, and form stones.

7. Hypertension: The mechanism of hypertension in obstructive nephropathy is the same as other renal hypertensive hypertension, caused by factors such as expansion of extracellular fluid volume, active renin-angiotensin system and decreased vasodilators, unilateral or bilateral After the obstruction is relieved, hypertension can be relieved by itself.

8. Polycythemia: erythrocytosis can be seen in renal tumors, renal cysts, polycystic kidney or hydronephrosis, obstructive nephropathy erythrocytosis is associated with increased erythropoietin synthesis and release.

9. Urinary ascites: In neonatal or infantile obstructive nephropathy, occasional spontaneous extravasation of urine into the abdominal cavity, causing urinary ascites, at this time ascites creatinine / serum creatinine ratio becomes 3:1, rather than urine ascites ratio For 1:1, this point is available for identification.

Pediatric urinary tract obstruction examination

Anemia is often secondary to uremia caused by chronic urinary tract infection or bilateral hydronephrosis. Increased white blood cells suggest active infection. In obstructive nephropathy, urine tests may be normal, but urine density and osmotic pressure are usually reduced. Red, leukocytosis; urine protein negative or small amount (<1.5g/24h), visible granules, transparent or waxy cast, white blood cell cast type suggesting urinary tract infection, bilateral renal effusion, urine in the renal tubule The flow rate is slowed down, urea reabsorption increases, and creatinine does not. The normal urine urea nitrogen/creatinine ratio is about 10:1. The ratio of bilateral hydronephrosis decreases. When the distal renal tubular acidosis exists, it appears high. Chlorine metabolic acidosis, in order to determine the location, etiology and severity of obstructive nephropathy, imaging techniques must be used:

1. Abdominal plain film (KUB)

The plain film can be seen in the outline of the kidney or calcification, which can help to find the kidney, ureteral positive stones, and understand the size of the kidney.

2. Intravenous pyelography (IVP)

Intravenous pyelography can understand bilateral renal and ureteral conditions, which is an examination that reflects the kidney, renal pelvis, renal pelvis and ureteral anatomy, and roughly reflects the renal function. Children routinely use 60% or 76% diatrizoate, Neonatal 8 ~ 10ml, <6 months 10 ~ 12ml, 6 ~ 12 months 12 ~ 15ml, and renal dysfunction, urea nitrogen up to 50mg / dl, instead of urinary closure, can increase the dose up to 2.2ml / kg Adding the same amount of glucose solution quickly, delaying the film, taking 60-120min to take the whole urinary tract film, can make satisfactory results in most cases. When the hydronephrosis is seen, the contrast agent stays in the enlarged renal pelvis, but when serum When the creatinine level is greater than 442 mol/L, the development is usually poor. This examination should not be selected. It is necessary to use renal puncture angiography to understand the obstruction site, but it must be performed separately to avoid renal failure.

3. Urinary bladder urethrography

In the diagnosis of children with lower urinary tract obstruction is very common, suspected of lower urinary tract obstruction, waiting for bladder filling before the end of angiography for urinary bladder urethra angiography, can show lesions.

(1) Method: The contrast agent can enter the bladder through three methods:

1 intravenous administration.

2 transurethral catheter to guide the human bladder, after injection, pull out the catheter, do urinary bladder urethra angiography, in the baby must press the bladder to do urinary bladder urethra angiography.

3 puncture injection through the suprapubic region.

(2) Note: Any method should pay attention to the following points:

1 When urinating, multiple times of photography should be performed to observe the presence or absence of vesicoureteral reflux. Because vesicoureteral reflux is not seen at every examination, it is necessary to take oblique slices.

2 Fill the bladder to its capacity to estimate the presence or absence of trabeculae. The bladder capacity (ml) of 5 to 13 years old = 146 ml + 6.1 × age, 75 ml for newborns and 300 ml for large children.

3 After the bladder is empty, pay attention to the problem of residual urine. The partial section of the urethra is best to use the oblique position. Its advantage is that the full length of the urethra can be seen when urinating, and the amount of radiation of the oblique testicle is the least.

4 Bladder urethrography should pay attention to the normal filling defect, that is, the internal sphincter is more obvious at the end of urination, and the normal sputum can also have filling defects.

4. Ultrasound examination

Because this test is non-invasive and does not depend on renal function, it is the first choice for the determination of renal pelvis and renal pelvis with or without water accumulation. The accuracy is greater than 90%, but the false positive rate of B-ultrasound is 8% to 26%. It is also impossible to determine the location and cause of obstructive nephropathy. It is a shortcoming. B-mode ultrasonography can assist in the location of urinary tract obstruction, such as proximal ureteral obstruction, ureteral dilatation, and lower urinary tract obstruction or distal ureteral obstruction. Flow, the ureter expands.

5. Radionuclide examination

Renal examination is a better way to understand the function of the lateral renal function. In addition to assisting the diagnosis of obstruction, it can understand the function of the kidney, but the location of the obstruction is poor. The diagnostic value of urinary dynamic imaging for obstruction is not as good as IVP, but this The technique uses only small doses of radionuclide, a systemic response without contrast agent, which can sensitively display residual renal function, which is helpful for understanding whether the patient's renal function can be restored or whether the kidney can be retained. During renal and urinary dynamic imaging examinations Intravenous injection of furosemide 0.3 ~ 0.5mg / kg, help to determine the presence or absence of mechanical obstruction.

6.CT

It is particularly useful for determining the location and cause of obstructive nephropathy, and there is a tendency to replace invasive retrograde pyelography. However, because CT is expensive, a larger amount of contrast agent is used, so it is not preferred.

7. Magnetic resonance imaging (MRI)

The advantages and disadvantages are similar to CT. Magnetic resonance water imaging (MRU) can clearly show the location of upper urinary tract obstruction. Urodynamics combined with X-ray examination is very important for the detection of some problems in lower urinary tract obstruction, such as bladder compliance. Sexual and bladder urethral muscle and urethral sphincter coordination.

8. Ureteral pyelography

It is divided into two types: antegrade and retrograde. The antegrade angiography is used for the above examinations. It is not clear that the pathological anatomical changes or renal excretion contrast agents are poor. Usually, B-ultrasound or CT-guided percutaneous puncture into the dilated renal pelvis, injection angiography. The agent is inspected. This technique is not only used for diagnosis, but also for treatment. Retrograde ureteral pyelography should be performed under cystoscopy. Cystoscopy is unique for observing posterior urethral and bladder lesions. Retrograde ureteral insertion under cystoscopy. Tubes, urine were collected from unilateral or bilateral ureters for analysis, and then contrast agents were injected to show ureter or ureteral obstruction.

Diagnosis and diagnosis of urinary tract obstruction in children

diagnosis

1. History and characteristics: Patients with typical medical history and signs have no difficulty in diagnosis, but sometimes the lesions have been hidden for many years without being discovered. Therefore, any patients with acute or chronic renal failure should pay attention to the presence or absence of obstructive nephropathy. Repeated urinary tract infections, patients with ineffective or relapsed medical treatment should be vigilant and carefully examined. Patients with previous kidney stones, gynecological diseases and surgery, intestinal diseases or their surgical history are also diagnostic clues.

2. Imaging examination: It is the main method of diagnosis.

Differential diagnosis

When urinary tract infection and reflux, when collecting water, you can pay attention to the exclusion of urinary tract obstruction, find urinary tract obstruction, through imaging methods and other methods to identify the location of obstruction and the cause of obstruction as soon as possible, in order to facilitate prognosis and effective treatment, First of all, you should pay attention to the medical history. When the child complains of abdominal pain or low back pain, it must be differentiated from acute abdomen. If the abdominal mass is prominent, it must be combined with other retroperitoneal masses such as nephroblastoma, teratoma and neuroblast. Identification of tumors, such as bladder neck irritation symptoms such as frequent urination, urgency and dysuria, should pay attention to urination, such as small urination, urination, prolonged urination, urination, etc., such as mobility in the bladder Obstruction, the urine flow can be suddenly interrupted, must do anal diagnosis, pay attention to the presence or absence of pelvic tumors and stones and anal sphincter, insert catheter to measure residual urine, and can exclude urethral stricture.

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