Pediatric Nephrology

·         In AGN, best test to determine cause is C3 & C4 level.

·         Only Shigella dysenteriae serotype 1 commonly produces Shiga toxin and causes HUS.

·         Chronic use of antibiotics is not a risk factor for urinary tract infection.

·         Multicystic dysplastic kidneys are not inherited. In contrast, polycystic kidneys are bilateral; inheritance is either autosomal dominant (adult) or autosomal recessive (child).

·         Segmental hypoplasia, or Ask-Upmark kidney, produces severe hypertension, usually beginning at age 10 yr when identified on routine examination. Nephrectomy is the treatment of choice.

·         Cystitis is not usually associated with fever. With fever, chills, or rigors, suspect pyelonephritis with or without urosepsis.

·         Oliguria is common in neonates during the first day of life because glomerular filtration is reduced. Nearly all babies will void, however, by 24 hours of life.

·         The creatinine measurement on the first day of life reflects the mother's creatinine level, whereas the 48-hour creatinine level is much more a reflection of neonatal renal function.

·         Normal urine output should exceed about 1 mL/kg/day in the neonatal period. Below that level can be considered oliguria after the first day of life. Polyuria can be considered when urine output exceeds 4-5 mL/kg/day.

·         Neonates cannot induce water intoxication through excessive water intake.

·         During the first 3 weeks of life, a premature infant can reduce the urine pH only to 6.0 ± 0.1. After 1 month, the urine pH can be reduced to 5.2 ± 0.4.

·         Ideally, if potassium supplementation or replacement is needed, the concentration of potassium in the intravenous fluids should not exceed 40 mEq/L if given via a peripheral vein or 80 mEq/L if given via a central vein. Infusion rates should not be >0.3 mEq K+/kg/h. Faster delivery can lead to local irritation of the veins, paresthesias and/or weakness, and cardiac arrest because of changes in transmembrane potentials. For life-threatening conditions that result from hypokalemia (e.g., cardiac dysrhythmias, respiratory paralysis in a patient without alkalosis or acidosis), the rate may be increased up to 1 mEq K+/kg/h given centrally by an infusion pump. A continuous electrocardiogram monitor should be in place.

·         ENURESIS

1. This is a very familial condition; 70% of enuretic children have a parent with the condition.
2. Nocturnal enuresis prevalence rates show a natural history of spontaneous resolution: 20% at 5 years, 10% at 7 years, and 5% at 10 years, with only a 1% persistence rate.
3. Isolated primary nocturnal enuresis rarely has identifiable organic pathology.
4. There is a high relapse rate when medications are stopped.
5. Enuresis alarms are the most therapeutically (especially in younger patients) and cost effective, but they require weeks of consistent use for full benefits.

·         Other than a timed urine collection, the best "spot" method for determining the degree of proteinuria is Urinary protein/creatinine excretion ratio. Thus, on a random sample of urine, a urine protein/creatinine ratio of <0.2-0.25 reflects a normal daily protein excretion, whereas values of >1 strongly suggest the presence of the nephrotic syndrome.

·         The key to orthostatic proteinuria is that protein excretion is truly normal when recumbent and the individual is otherwise entirely healthy.

·         GFR: Use of the Schwartz formula requires only a serum creatinine level and the height of the child. No urine collection, timed or untimed, is necessary. The formula is as follows:

Creatinine clearance (mL/min/1.73m2) = K × Height (cm)/Serum creatinine (mg/dL)

K is 0.45 in infants <1 year old, 0.55 in infants >1 year old, 0.33 in low birthweight infants, and 0.7 in adolescent males.

·         The Clinitest tablet detects reducing substances in the urine. These include reducing sugars (e.g., glucose, galactose, lactose, pentoses, fructose) and other compounds, including high amounts of amino acids, oxalate, ketones, and uric acid. It is also positive in the presence of many drugs, including high concentrations of ascorbic acid, penicillin, cephalosporins, nitrofurantoin, sulfonamides, and tetracycline. The glucose oxidase square on the dipstick is specific for glucose. The Clinitest may be helpful as an initial screening tool for a child who is suspected of having galactosemia, or it may be useful when testing the stool of a child who is suspected of having carbohydrate malabsorption/intolerance.

·         Most effective means of minimizing pain in circumcision are a ring block or a dorsal penile nerve block. The latter consists of injecting 0.3-0.4 mL of 1% lidocaine without epinephrine in both sides of the dorsal penile base.

·         UAG is negative in RTA 2, positive in RTA 1,3,4.

·         If a urine specimen cannot be processed within 15 minutes, it should be refrigerated at <4°C to stop in vitro replication.

·         The use of cranberry juice as a urine-acidifying agent and treatment for UTI has been popular for adults since the 1920s, and studies of adults have shown it to be helpful for diminishing the frequency of bacteriuria, possibly because of its antiadhesive properties against Escherichia coli.

·         The strict definition of hypercalciuria in a child is >4 mg of urinary calcium per kilogram per 24 hours on an unrestricted diet that is normal for the child's age. Twenty-four hour urine collections can be difficult in young children. Therefore, random urine collections have been used to screen for hypercalciuria. The urine calcium/creatinine ratio will vary with age.

·         Bladder exostrophy is caused by a persistence of the cloacal membrane after the fourth gestational week and a lack of medial migration of the lateral mesoderm.