Campbell-Walsh Urology, 11th Edition

PART XV

Pediatric Urology

SECTION A

Development and Prenatal Urology

123

Renal Functional Development in Children

Victoria F. Norwood; Craig A. Peters

Questions

1. A 2-month-old infant born at 32 weeks gestation is expected to have:
2. completed nephrogenesis but immature renal functional abilities.
3. incomplete nephrogenesis and immature renal functional abilities.
4. completed both nephrogenesis and renal functional maturation.
5. functionally mature nephrons but ongoing formation of additional nephrons.
6. no increased risk of chronic kidney disease (CKD) compared to an infant born at 38 weeks gestation.
7. A 2-week-old boy with bilateral moderate hydronephrosis who was born at 30 weeks gestation is found to have a serum creatinine of 0.7 mg/dL. This would suggest:
8. significant renal dysfunction, possibly due to posterior urethral valves.
9. maternal renal function.
10. moderate renal dysfunction unrelated to his hydronephrosis.
11. normal renal function without evidence of obstruction.
12. likely hemolyzed specimen with inaccurate creatinine level.
13. A 4-year-old boy presents with swelling and decreased urine output. He has had eyelid edema on awakening for the past week. His blood pressure is 90/50 mm Hg, and he has marked eyelid edema, distended abdomen, and pitting edema of the legs and feet. Urinalysis showed a specific gravity of 1.030, pH 5, 3 + protein, and trace of blood. Serum studies show a sodium level of 131 mEq/L, blood urea nitrogen value of 30 mg/dL, creatinine level of 0.3 mg/dL, and albumin level of 1.6 g/dL. The appropriate next step in management is:
14. quantitation of urinary protein excretion, renal ultrasound, and lipid panel.
15. initiation of oral prednisone.
16. workup for occult malignancy.
17. quantitation of urinary protein excretion, renal ultrasound, lipid panel, and initiation of prednisone therapy.
18. quantitative protein excretion, lipid panel, and prednisone therapy.
19. A 6-year-old, healthy girl undergoes a routine physical examination. Urinalysis reveals a specific gravity of 1.020, pH 6, trace protein, and moderate amount of blood on dipstick testing. The microscopic test shows 5 to 6 red blood cells per high-powered field. An inappropriate next step is:
20. renal ultrasonography.
21. random urine calcium and creatinine determinations.
22. clean-catch urine culture.
23. an empirical 10-day course of antibiotics.
24. a repeat urinalysis in 2 weeks.
25. A urinalysis in an 8-year-old boy shows a specific gravity of 1.030, pH 5, trace protein, and moderate amount of blood. He has a normal physical examination, including blood pressure of 96/56 mm Hg. On further history he was hospitalized 2 months ago with poststreptococcal glomerulonephritis. The most appropriate course of action is:
26. cystoscopy.
27. renal ultrasonography.
28. a course of antibiotics after obtaining a urine culture.
29. to reassure his family and obtain records from the outside institution.
30. computed tomography (CT).
31. A 6-year-old boy is seen in the emergency department with the new onset of left-sided flank pain, gross hematuria, and vomiting. His blood pressure is 120/70 mm Hg, and the physical examination reveals right costovertebral angle tenderness. The urinalysis shows brown urine with a specific gravity of 1.030, pH 7, large amount of blood, and 2 + protein. The next step in diagnostic evaluation should NOT include:
32. high-resolution CT of abdomen/pelvis without contrast.
33. microscopic examination of the urine.
34. cystoscopy.
35. renal ultrasonography.
36. serum electrolyte determination.
37. An 8-year-old is seen in the emergency room with 24 hours of severe left flank pain and nausea. Urinalysis shows a specific gravity of 1.024, pH of 6.3, and a serum creatinine of 0.4 mg/dl. He is afebrile and has had no surgery. The most appropriate next step is:
38. no further imaging is needed.
39. double-J ureteral stent placement.
40. hospital admission and 4 days of antibiotics.
41. abdominal ultrasound.
42. CT urogram with and without contrast.
43. A 9-year-old girl presents after passing a 3-mm stone. On analysis, the stone is composed 100% of calcium oxalate. The next step is to:
44. start a thiazide diuretic.
45. obtain a 24-hour urine collection to test for calcium, creatinine, oxalate, and citrate.
46. start potassium citrate.
47. restrict dietary calcium.
48. restrict dietary oxalate.
49. A 6-year-old boy is seen in the emergency department with new onset of headache and gross hematuria. He has no dysuria or fever but has vomited three times. He had a sore throat the week before, but it has resolved. His blood pressure is 140/90 mm Hg, and physical examination reveals a heart murmur. The urinalysis shows brown urine with a specific gravity of 1.030, pH 7, large amount of blood, and 2 + protein. The next step in the diagnostic evaluation should include all of the following EXCEPT:
50. CT of the abdomen and pelvis.
51. comprehensive metabolic panel.
52. C3 determination.
53. antistreptolysin O titer.
54. microscopic examination of the urine.
55. A 3-year-old boy is seen in the emergency department with a respiratory problem and gross hematuria. He has no dysuria or abdominal pain but has fever, rhinorrhea, and cough. His blood pressure is 120/70 mm Hg, and physical examination shows rhinorrhea, mild pharyngeal erythema, and no peripheral edema or abdominal tenderness. The urinalysis shows brown urine with a specific gravity of 1.030, pH 7, large amount of blood, and 2 + protein. (His mother also has had hematuria in the past, and his maternal uncle is deaf and on hemodialysis.) The next step in diagnostic evaluation includes all of the following EXCEPT:
56. renal biopsy.
57. antistreptolysin O titer and C3.
58. comprehensive metabolic panel.
59. microscopic examination of the urine.
60. CT of the abdomen and pelvis.
61. A 16-year-old boy with end-stage renal disease is managed with peritoneal dialysis (PD). He develops abdominal pain, vomiting, and a fever of 100.9° F. The next step in management is to:
62. obtain blood and urine cultures.
63. start broad-spectrum antibiotics.
64. collect a specimen of dialysate for white blood cell count and culture.
65. change to hemodialysis.
66. administer intraperitoneal antibiotics.
67. During an evaluation for ongoing malaise and poor appetite, which followed initiation of treatment for otitis media four earlier, an 8-year-old boy is found to have a blood urea nitrogen level of 40 mg/dL and a creatinine of 1.4 mg/dL. His urinary sodium level is 13 mEq/L, fractional excretion of sodium (FE_Na) is 0.8%, and urinary osmolality is 410 mOsm/Kg. The most likely cause of his renal insufficiency is:
68. posterior urethral valves.
69. dehydration
70. interstitial nephritis.
71. hemolytic uremic syndrome.
72. previously unknown bilateral ureteropelvic junction obstruction.
73. A 9-year-old boy is found during routine examination to have a blood pressure of 120/90 mm Hg. The child was calm, and a properly sized blood pressure cuff was used for the measurement. The best next step in management is to:
74. repeat the measurement next week in the office.
75. obtain a fasting lipid profile.
76. perform renal ultrasonography.
77. obtain peripheral vein renin levels.
78. perform ambulatory blood pressure monitoring (ABPM).
79. An otherwise healthy 14-year-old boy is found to have 2 + protein on a urinalysis obtained as part of a sports physical for football. The most appropriate initial step in the evaluation should be:
80. referral to the first available pediatric urologist or nephrologist.
81. renal ultrasound, serum chemistries, and 24-hour urine protein quantitation.
82. initiation of oral prednisone.
83. spot protein and creatinine ratio on a first morning void following rest.
84. repeat urinalysis ASAP.
85. A 5 year-old-boy with posterior urethral valves since birth has renal function that has slowly declined to a current creatinine of 1.7 mg/dl. His growth is impaired with height and weight less than the third percentile. The most appropriate management strategy is:
86. referral to the nearest transplant program for initiation of transplant evaluation.
87. collaboration with a pediatric nephrologist about management of CKD.
88. repeat urodynamics in expectation of preemptive transplantation.
89. initiation of bicarbonate and growth hormone.
90. repeat valve ablation.
91. A 13-year-old boy presents with intermittent left flank pain and microscopic hematuria. Ultrasound shows bilateral renal calculi without evidence of obstruction. Urinalysis shows moderate RBCs, no WBCs, pH of 6.3, and hexagonal-shaped crystals. CT imaging demonstrates the calculi, which are found to have a Hounsfield density of 420 HU. The most appropriate initial therapy for this boy would be:
92. bilateral percutaneous nephrolithotomy.
93. bilateral ureteroscopic lithotomy.
94. urinary acidification and repeat imaging.
95. treatment with allopurinol.
96. treatment with dimercaptoproprionylglycine.

Answers

1. b. Incomplete nephrogenesis and immature renal functional abilities.Nephrogenesis completes by 34 to 36 weeks postconception, whether in utero or ex-utero. Functional maturation continues for at least one year. Infants born prematurely most likely do not achieve their genetic endowment of normal nephrons and are at higher risk of developing CKD throughout life compared to infants born at term.
2. d. Normal renal function without evidence of obstruction.A serum creatinine of 0.7 mg/dl is within normal range for a premature infant. The moderate degree of hydronephrosis is unlikely to suggest obstruction severe enough to cause an elevated creatinine. While it is reasonable to rule out posterior urethral valves, the absence of dilated ureters would suggest it is of low likelihood.
3. d. Quantitation of urinary protein excretion, renal ultrasound, lipid panel, and initiation of prednisone therapy.The patient has hypoalbuminemia, edema, and proteinuria and most likely has nephrotic syndrome. In the absence of profound anasarca, the initial illness may be managed in the outpatient setting. Completion of diagnostic studies (quantitation of urinary protein, measurement of plasma lipids, and other studies as indicated), family education, and institution of a low-salt diet are followed by initiation of oral prednisone. A renal biopsy is not indicated if minimal change nephrotic syndrome is likely. Oral diuretics are not commonly prescribed unless careful observation is possible. Malignancy is very rarely associated with nephrotic syndrome in children. Renal ultrasonography only occasionally adds additional significant information but is usually performed at some point during the evaluation. Most children with primary nephrotic syndrome respond to corticosteroids within 14 days and have spontaneous diuresis with loss of edema and proteinuria.
4. d. An empirical 10-day course of antibiotics.Although asymptomatic hematuria may be caused by occult urinary tract infection, empirical treatment without culture is never the correct approach. Unfortunately this scenario happens far too frequently. It is reasonable to repeat the urinalysis before proceeding with diagnostic evaluation. If the hematuria persists, imaging the kidneys and urinary tract and screening for hypercalciuria is a reasonable approach.
5. d. To reassure his family and obtain records from the outside institution.Given the previous history of postinfectious glomerulonephritis (in his case because of a preceding streptococcal infection), the most likely cause of microscopic hematuria is resolving nephritis. The microhematuria may persist for up to 1 year, while the proteinuria and macroscopic hematuria usually resolve within the 2-week acute phase. It would be helpful to confirm the diagnosis with review of medical records.
6. c. Cystoscopy.The clinical picture is that of a child presenting with a renal calculus. Cystoscopy is rarely indicated in the diagnostic evaluation, although it might be included during the treatment phase of nephrolithiasis in children. High-resolution CT without administration of a contrast agent is the test of choice, but one cannot argue that ultrasonography should be the first test. Examination of the urine is also a viable first step because children with nephritis occasionally complain of flank pain. Serum electrolytes would not be diagnostic of stone disease but could be helpful if vomiting has been significant.
7. d. Abdominal ultrasound.This clinical scenario is most consistent with acute presentation of a renal or ureteral stone. Ultrasound imaging to rule out hydronephrosis and to, often, reveal the stone is the best first step. Intervention for drainage is not indicated until appropriate analgesics have been initiated. CT imaging is unlikely to add further information and exposes the child to radiation.
8. b. Obtain a 24-hour urine collection to test for calcium, creatinine, oxalate, and citrate. A metabolic evaluation for the cause of calcium oxalate nephrolithiasis should be initiated because the differential diagnosis includes hyperoxaluria, hypercalciuria, renal tubular acidosis, or idiopathic calcium stones. In children, preventative treatment is rarely initiated without attempts to diagnose the underlying metabolic disturbance. Dietary calcium restriction below the recommended daily allowance is never a treatment for children with calcium stones with or without hypercalciuria.
9. a. CT of the abdomen and pelvis. With symptomatic hypertension and gross hematuria, one must entertain the possibility of acute glomerulonephritis. The prior history of pharyngitis is consistent with poststreptococcal-associated disease. Examination of the urine sediment for signs of glomerulonephritis (cellular casts) and documentation of renal function and electrolytes as well as elevated antistreptolysin O titer and decreased C3 are the usual steps taken to confirm the diagnosis. Hypertension is treated aggressively with salt restriction, loop diuretics, and antihypertensive agents. Resolution of the hypertension parallels resolution of the acute phase.
10. e. CT of the abdomen and pelvis.The presentation of gross hematuria during a respiratory infection is not characteristic of postinfectious glomerulonephritis because the onset of nephritis usually follows the infection. The positive family history is important because the onset of macroscopic hematuria during a respiratory infection is characteristic of two forms of chronic glomerulonephritis: (1) IgA nephropathy and (2) Alport hereditary nephritis. Imaging with ultrasound does not usually add to diagnostic accuracy but is often performed at some point, even if glomerulonephritis can be confirmed by microscopic examination of the urine. Patients with either IgA or hereditary nephritis would be expected to have normal C3. A renal biopsy is needed for diagnosis of IgA and is usually needed for diagnosis of hereditary nephritis, except in the case in which an affected relative has already undergone biopsy.
11. c. Collect a specimen of dialysate for white blood cell count and culture. Peritonitis is the most common complication of PD. Although the patient may undergo a full fever workup including urine and blood cultures as directed by the severity of the clinical presentation, the diagnosis of peritonitis is secured by collecting a sample of dialysate, which is often cloudy, and finding 100 WBCs/mm³, of which 50% are neutrophils. Antibiotics will be administered after the cultures are collected. PD can continue while treating the peritonitis.
12. b. Dehydration.The biochemical analysis that was provided indicates a prerenal cause of acute renal injury. Prerenal azotemia may be present in the earliest phases of hemolytic uremic syndrome if volume depletion is present, but a diarrheal prodrome is expected. Posterior urethral valves, interstitial nephritis, and bilateral ureteropelvic junction obstruction are all associated with salt-wasting and impaired urinary concentrating ability.
13. a. Repeat the measurement next week in the office.This child’s blood pressure is elevated, and measurement should be repeated and hypertension confirmed. ABPM could be considered but is recommended in children older than 10 years and is more practically performed after repeated office measurements. Therefore the blood pressure should be remeasured in the office. If hypertension is confirmed, the workup will include a complete metabolic panel, lipid profile, echocardiogram, and renal ultrasonography. Angiography and selective renin levels would be performed in the case of severe or recalcitrant hypertension.
14. d. Spot protein and creatinine ratio on a first morning void following rest. Low-grade proteinuria in an otherwise healthy teen, especially an athlete, is most likely either exercise-induced transient proteinuria or orthostatic proteinuria, both of which are benign. A first morning void, carefully collected to avoid contamination with urine from activities the day before (i.e., bladder was emptied prior to bed the night before) and quantitated by spot urine protein:creatinine ratio is the most efficient first step. If there is no significant protein on that sample (urine P:C < 0.2) then no further workup or specialty referral is needed.
15. b. Collaboration with a pediatric nephrologist about management of CKD.Children with CKD from urologic disorder, even stage I with normal GFR, are best managed in a collaborative multi-specialty environment led by a team of urology and nephrology providers. Prevention, as opposed to treatment, of growth failure (as well as other sequelae of CKD) is imperative and generates the best possible foundation for successful renal transplantation and long-term outcome.
16. e. Treatment with dimercaptoproprionylglycine.The presence of bilateral low-density stones with crystalluria consistent with cystine in an adolescent is most likely that of cystinuria. While uric acid stones would be possible and urinary metabolic evaluation is appropriate, the most likely diagnosis is cystinuria. Initial surgical treatment would be appropriate for uncontrolled pain, obstruction or infection (Patel et al, 2014).*

Chapter Review

1. Nephrogenesis is not complete until 36 weeks in utero; two-thirds of the nephrons develop in the third trimester.
2. At the time of birth, GFR is about 10% of the adult value. It is dependent upon gestational age and doubles in the first two weeks of life.
3. Serum creatinine at birth reflects maternal creatinine; by 1 to 3 months it should decrease to about 0.3 mg/dl.
4. Neonatal concentrating ability, the ability to excrete a large fluid load, the ability to conserve sodium, and the ability to excrete potassium and to acidify the urine are all limited in the newborn and take between six months and one year to approach the normal adult capabilities. These abnormalities are even more pronounced in the premature infant.
5. Normal fractional excretion of sodium for an infant is 1% to 3%; for an adult, it is less than 1%.
6. Normal serum bicarbonate in an infant is 15 to 18 mM/L due to the physiologic limitations for acidification.
7. Water makes up 80% of the body weight of the newborn.
8. Fetal urine output is required for normal alveolar development in utero.
9. Isotonic saline is usually used as the maintenance fluid in hospitalized children.
10. Isolated microscopic hematuria in children is usually benign; gross hematuria has a defined etiology in two-thirds of patients.
11. Hematuria in the presence of significant proteinuria indicates glomerular disease.
12. Hypercalciuria is one of the most common causes of recurrent or persistent microscopic hematuria.
13. Hypercalciuria may be diagnosed by a calcium: creatinine ratio greater than 0.2 mg or a 24-hour calcium excretion exceeding 0.4 mg/Kg.
14. Normal urinary protein excretion in a child is less than 100 mg/meter²/day
15. The etiology of proteinuria may be divided into three categories: (1) an abnormality of glomerular permeability, (2) tubule dysfunction, and (3) excessive plasma protein concentrations.
16. Proteinuria is characterized as transient, orthostatic, or fixed.
17. Reflux nephropathy may result in proteinuria.
18. Fanconi syndrome is a generalized dysfunction of the proximal renal tubule.
19. Type 4 RTA is a distal RTA associated with hyperkalemia, defective NH4 metabolism, and aldosterone resistance. It is most commonly seen with obstructive uropathy or multicystic dysplasia.
20. Polydipsia, polyuria, and poor growth are common features of renal tubule disorders.
21. The most common cause of acquired nephrogenic diabetes insipidus is obstructive uropathy. Other causes include lithium and amphotericin administration.
22. Hypercalciuria is the most common cause of stones in children.
23. Metabolic causes of stone disease in children include: (1) type I RTA (calcium stones), (2) primary hyperoxaluria (calcium oxalate stones), (3) cystinuria (cystine stones), and (4) Lesch-Nyhan syndrome (uric acid stones).
24. Inflammatory bowel disease, prematurity, the use of lasix, the use of steroids, malignancy, and genetic abnormalities should be considered in the etiology of stone disease in children.
25. A significant cause of hypertension in children is obesity.
26. The most common cause of acute kidney injury in children is systemic illness or its treatment.
27. Acute kidney injury is an independent risk factor for mortality.
28. The etiology of end stage renal disease in children is renal cystic, hereditary, or congenital disorders in 36% of cases.
29. Uncorrected acidosis in children results in retardation of linear growth and decreased bone mineralization.
30. Preemptive transplantation prior to the initiation of dialysis is the goal for all children with CKD.

^* Sources referenced can be found in Campbell-Walsh Urology, 11th Edition, on the Expert Consult website.