Kidney and Urinary Tract Disorders PDF

Kidney and urinary tract disorders Features of kidney and urinary tract disorders in children: Many structural abnormalities of the kidneys and urinary tract are identified on antenatal ultrasound screening. Urinary tract infection, vesicoureteral reflux, and urinary obstruction have the po...

Kidney and urinary tract disorders Features of kidney and urinary tract disorders in children: Many structural abnormalities of the kidneys and urinary tract are identified on antenatal ultrasound screening. Urinary tract infection, vesicoureteral reflux, and urinary obstruction have the potential to damage the growing kidney. Nephrotic syndrome is usually steroid sensitive and only rarely leads to chronic kidney disease. Chronic renal disorders may affect growth and development. Assessment of renal function The kidney has multiple functions: 1. filtering water-soluble salts and ions from the blood whilst not filtering out large molecules 2. the reabsorption of necessary filtered small molecules, such as glucose and amino acids 3. the dilution or concentration of urine to optimize fluid balance 4. the regulation of blood pressure 5. the metabolism of vitamin D 6. the regulation of acid–base balance. The assessment of ‘renal function’ is done by: Plasma creatinine (a product of muscle breakdown) – is generally used to assess and monitor renal function. However, the normal range of serum creatinine increase throughout childhood, accompanying increasing muscle mass and height. Creatinine level does not become abnormally high until renal function is markedly reduced. Plasma urea – is raised in acute kidney injury and chronic kidney disease and increases before the rise in creatinine. However, it is not as specific as it also rises in dehydration, catabolic states, high protein diet and gastrointestinal bleeding. High urea levels may cause nausea, vomiting and headaches. Estimating glomerular filtration rate – is a more accurate way of monitoring renal function (GFR) is low in the newborn infant and is especially low in premature infants; the GFR at 28 weeks’ gestation is only 10% of the term infant. In term infants, the corrected GFR (20–30 ml/min) Formal GFR measurement – is performed measuring clearance of a substance that is freely filtered by the glomerulus and not reabsorbed by the tubules. Inulin is now used in the UK but involves intravenous administration of inulin followed by serial blood tests to measure its clearance. Formal GFRs are not routinely used, Urinary protein loss – occurs before the fall in GFR in chronic kidney disease. Urine osmolality is an indicator of how well the kidneys can concentrate the urine and hence how well they are functioning. Radiological investigations of the kidneys and urinary tract Congenital anomalies Since the introduction of antenatal ultrasound screening, most significant structural congenital anomalies of the kidneys and urinary tract (CAKUT) are identified antenatally and are managed prospectively. They are potentially important because they may:  be associated with abnormal renal development or function (chronic kidney disease)  predispose to urinary tract infection   involve urinary obstruction which requires surgical treatment  be associated with non-renal congenital anomalies. The antenatal detection and early treatment of urinary tract anomalies provide an opportunity to minimize or prevent progressive renal damage. However, minor abnormalities are also detected, most commonly mild unilateral pelvic dilatation, which does not require intervention but may lead to over-investigation, unnecessary treatment, and unwarranted parental anxiety. 1. Absence of both kidneys (renal agenesis) – As amniotic fluid is mainly derived from fetal urine, there is severe oligohydramnios resulting in Potter sequence ( which is fatal due to failure of development of fetal lungs. 2. Multicystic dysplastic kidney (MCDK)  Results from the failure of union of the ureteric bud (which forms the ureter, pelvis, calyces, and collecting ducts) with the nephrogenic mesenchyme.  It is a non-functioning structure with large fluid-filled cysts with no renal tissue and no connection with the bladder Half will have involuted by 2 years of age,  and nephrectomy is indicated only if it remains very large or hypertension develops, but this is rare.  MCDKs do not produce urine and, if they are bilateral, Potter sequence will result. 3. Cystic dysplastic kidneys  can be caused by autosomal recessive polycystic kidney disease or autosomal dominant polycystic kidney disease, and renal cysts and diabetes.  In contrast to a multicystic dysplastic kidney, in these disorders some or normal renal function is maintained but both kidneys are always affected.  the main symptom in childhood is hypertension,  and it causes chronic kidney disease requiring renal replacement in late adulthood. It is associated with several extrarenal features including cysts in the liver and pancreas, cerebral aneurysms, and mitral valve prolapse. 4. A pelvic kidney or a horseshoe kidney when the lower poles are fused in the midline, result from abnormal caudal migration of the kidneys. The abnormal position may predispose to infection or obstruction of urinary drainage. 5. Duplex kidneys  can vary from simply a bifid renal pelvis to complete division with two ureters.  These ureters may have an abnormal drainage so that the ureter from thelower pole moiety often refluxes, whereas the upper pole ureter may drain ectopically into the urethra or vagina or may prolapse into the bladder (ureterocele) and urine flow may be obstructed  6. (bladder exstrophy) Failure of fusion of the infraumbilical midline structures  results in exposed bladder mucosa.  Absence or severe deficiency of the anterior abdominal wall muscles is frequently associated with a large bladder and dilated ureters (megacystis–megaureter) and cryptorchidism,the prune- belly syndrome Urinary tract obstruction  Obstruction to urine flow may occur at the pelvi-ureteric or vesicoureteric junction, at the bladder neck (e.g. due to disruption of the nerve supply, neuropathic bladder), or at the posterior urethra in a boy due to mucosal folds or a membrane, known as posterior urethral valves.  At worst, this results in a dysplastic kidney which is poorly functioning, and may contain cysts.   In the most severe and bilateral cases Potter sequence is present. Renal dysplasia can also occur in association with severe intrauterine vesicoureteric reflux (VUR), in isolation, or associated with rare syndromes affecting multiple systems, e.g. VACTERL Thickened (b) with diverticula junction Posterior obstruction hydronephrosis. pelviureteric junction obstruction.  (vertebral, anorectal, cardiac, tracheoesophageal fistula, esophageal atresia, renal and limb abnormalities). Prophylactic antibiotics may be started at birth to try to prevent urinary tract infection (UTI), although practice varies between centres. As the newborn kidney has a low GFR, urine flow is low and mild outflow obstruction may not be evident in the first few days of life. The ultrasound scan should therefore be delayed for a few weeks. However, bilateral hydronephrosis in a male infant warrants investigations including an ultrasound and micturating cystourethrogram (MCUG) shortly after birth to exclude posterior urethral valves, which always requires urological intervention such as cystoscopic ablation  An example of a protocol for the management of infants with antenatally diagnosed urinary tract anomalies. MCUG, micturating cystourethrogram Vesicoureteric reflux VUR is a developmental anomaly of the vesicouretericjunctions. The ureters are displaced laterally and enter directly into the bladder rather than at an angle, with a shortened or absent intramural course.  Severe cases may be associated with renal dysplasia. It may be familial (30%–50% in first-degree relatives), occur temporarily after a urinary tract infection (UTI) or occur with bladder pathology, e.g. a neuropathic bladder or urethral obstruction. Its severity varies significantly ‫ز‬Mild reflux often resolves with age, but VUR that is severe enough to cause dilatation of the ureter may have significant longterm impact: 1. Urine returning to the bladder from the ureters after voiding results in incomplete bladder emptying, which encourages infection. 2. The kidneys may become infected (pyelonephritis) if reflux is severe enough to reach the kidney. 3. Bladder voiding pressure is transmitted to the renal papillae which may contribute to renal damage if voiding pressures are high 4. Infection may damage renal tissue, leaving a ‘scar’, resulting in a shrunken, poorly functioning segment of kidney (reflux nephropathy). 5. If scarring is bilateral and severe, progressive chronic kidney disease may develop. Progressive scarring needs an  assessment of the bladder and may be an indication for surgical intervention. 6. There is increased risk of hypertension in childhood or early adult life, which is estimated to be up to 10%. Urinary tract infection (UTI) UTI in childhood is important because:  up to half of patients have a structural abnormality of their urinary tract  pyelonephritis may damage the growing kidney by forming a scar, predisposing to hypertension and to progressive chronic kidney disease if the scarring is bilateral.  Risk factors of UTI: 1. Female 2. Uncircumcised male 3. +ve family history 4. Urinary obstruction 5. VUR 6. Catheterization 7. Sexual abuse Incomplete bladder emptying – may be because of constipation, infrequent voiding, resulting in bladder enlargement, neuropathic bladder or vesicoureteric reflux. Clinical picture In infants, symptoms are non-specific; fever is usually but not always present, and septicaemia may develop rapidly. As infants and toddlers cannot articulate their symptoms, the classical symptoms of dysuria, frequency, and loin pain only become evident with increasing age Dysuria alone is usually due to cystitis, or vulvitis in girls or balanitis in boys. Dysuria can also be secondary to bladder neck compression from constipation. Symptoms suggestive of a UTI may also occur following sexual abuse N.B A urine sample should be tested in all infants with an unexplained fever >38°C. Collection of samples The most common error in the management of UTI inchildren, and especially in infants, is failure to establish the diagnosis properly in the first place. If the diagnosis of a UTI is not made, the opportunity to prevent renal damage may be missed. UTI is also easily overdiagnosed by overzealous interpretation of urine dipstick results and contamination of urine samples on collection; this results in unnecessary treatment and investigation.  a ‘clean-catch’ sample best for infants  adhesive plastic bag applied to the perineum after careful washing, there may be contamination from the skin or faeces  urethral catheter if there is urgency  suprapubic aspiration used in severely ill infants  In the older child, urine can be obtained by collecting a midstream sample. Careful cleaning and collection are necessary  A bacterial culture of more than 105 colony-forming units (CFU) of a single organism/ml in a properly collected specimen gives a 90% probability of infection. If the same result is found in a second sample, the probability rises to 95%. A growth of mixed organisms usually represents contamination, but if there is doubt, another sample should be collected. Any bacterial growth of a single organism per millilitre in a catheter sample or suprapubic aspirate is considered diagnostic of infection.  UTI is usually the result of bowel flora entering the urinary tract via the urethra, although it can be haematogenous, e.g. in the newborn. The most common organism is Escherichia coli, followed by Klebsiella, Proteus, Pseudomonas, and Enterococcus faecalis.  Proteus infection is more commonly diagnosed in boys than in girls, possibly because of its presence under the prepuce. Proteus infection predisposes to the formation of phosphate stones by splitting urea to ammonia, and thus alkalinizing the urine.  Pseudomonas infection may indicate the presence of some structural abnormality in the urinary tract affecting drainage, and it is also more common in children with plastic catheters and ureteric stents. Investigation U/S+ DMSA scan/ MAG3 scan Done in these cases:  seriously ill or septicaemia  poor urine flow  abdominal or bladder mass  raised creatinine  failure to respond to suitable antibiotics within 48 hours  infection with atypical (non-E. coli) organisms. urethral obstruction is suspected on ultrasound (abnormal bladder in a boy), MCUG should be performe promptly. Functional scans  (i.e. DMSA or MAG-3) should be deferred for 3 months after a UTI, unless the ultrasound is suggestive of obstruction, to avoid missing a newly developed scar and because of false-positive results from transient inflammation. The need for any investigations in a child with only bladder symptoms (lower UTI/cystitis) I also controversial. Management 🌟< 3 M —> IV co-amoxiclav for 5-7 d then oral prophylaxis 🌟> 3M + Upper UTI ( loin pain or fever >38) —> IV co-amoxiclav 2-4 d then oral 10d (Trimethoprim) 🌟Lower UTI —> oral 5 d ( nitrofurantion- trimethoprim) Medical measures for the prevention of UTI  high fluid intake to produce a high urine output regular voiding ensure complete bladder emptying by encouraging the child to try a second time to empty his bladder after a minute or two, commonly known as double voiding, which empties any urine residue or refluxed urine returning to the bladder treatment and/or prevention of constipation good perineal hygiene Lactobacillus acidophilus, a probiotic to encourage colonization of the gut by this organism and reduce the number of pathogenic organisms that might potentially cause invasive disease antibiotic prophylaxis. This is controversial as evidence that giving antibiotic prophylactically to prevent infection is better than prompt treatment is lacking. They are often given in children under 2 years to 3 years of age with a congenital abnormality of the kidneys or urinary tract, following an upper UTI or those with severe reflux until out of nappies. Low-dose trimethoprim is used most often, but nitrofurantoin or cephalexin may be given. Broad-spectrum, poorly absorbed antibiotics such as amoxicillin should be avoided. Follow-up of children with recurrent UTIs, renal scarring, or reflux In these children: Urine should be dipsticked with any non-specific illness in case it is caused by a UTI and urine sent for microscopy and culture if suggestive of UTI. Consider prophylaxic oral antibiotics to reduce infections although breakthough infection can still occur. Circumcision in boys may sometimes be considered as there is evidence that it reduces the incidence of UTI. Bladder urodynamics assessment can detect incomplete bladder emptying or neuropathic bladder which may require intermittent clean catheterization to reduce risk of infections. Anti-VUR surgery may be indicated if there is progression of scarring with ongoing higher grade VUR. Blood pressure should be checked annually if renal dysplasia and scars are present. Urinalysis is performed to check for proteinuria which is indicative of progressive chronic kidney disease.  Regular assessment of renal growth and function is necessary if there are bilateral defects because of the risk of progressive chronic kidney disease.  Enuresis Daytime enuresis This is a lack of bladder control during the day in a child old enough to be continent (over the age of 3–5 years) Causes: 1. lack of attention to bladder sensation: a manifestation of a developmental or behavioural problem, although it may occur in otherwise normal children 2. detrusor instability (sudden, urgent urge to void induced by sudden bladder contractions 3. bladder neck weakness  4. a neuropathic bladder (bladder is enlarged and fails to empty properly, irregular thick wall, and is associated with spina bifida and other neurological conditions) 5.UTI (rare) 6. constipation 7. an ectopic ureter causes constant dribbling and child is always damp  Examination may reveal evidence of a neuropathicbladder, i.e. the bladder may be \distended, there may be abnormal perineal sensation and anal tone, or abnormal leg reflexes and gait. Sensory loss in the distribution of the S2, S3, and S4  An ultrasound may show bladder pathology, with incomplete bladder emptying or thickening of the bladder wall. Urodynamic studies may be required. An X-ray of the spine may reveal a vertebral anomaly. An MRI scan may be required to confirm or exclude a spinal defect such as tethering of the cord.  Affected children in whom a neurological cause has been excluded may benefit from star charts, bladder training, and pelvic floor exercises. Constipation shouldbe treated  Anticholinergic drugs, such as oxybutynin, to dampen down bladder contractions, may be helpful if other measures fail. Secondary (onset) nocturnal enuresis The loss of previously achieved urinary continence may be due to:  emotional upset, which is the most common cause  UTI  polyuria from an osmotic diuresis in diabetes mellitus or a renal concentrating disorder, Investigation should include:  testing a urine sample for infection, glycosuria, and proteinuria using a dipstick   assessment of urinary concentrating ability by measuring the osmolality of an early morning urine sample.  U/S Renal masses An abdominal mass identified on palpating the abdomen should be investigated promptly by ultrasound scan. . Bilaterally enlarged kidneys in early life are most Unilateral frequently due to autosomal Multicystic dysplastic kidney Compensatory hypertrophy of normal kidney recessive polycystic kidney Obstructed hydronephrosis disease (ARPKD), which is Renal tumour (Wilms tumour) Renal vein thrombosis associated with Bilateral hypertension, hepatic fibrosis, and progression to Autosomal recessive polycystic kidneys Autosomal dominant polycystic kidneys chronic kidney disease. Tuberous sclerosis Renal vein thrombosis  This form of polycystic kidney disease must be distinguished from ADPKD (autosomal dominant polycystic kidney disease), which has a more benign prognosis in childhood with onset of progressive chronic kidney disease in adulthood, although hypertension is found in at least 30% of affected children.