Pediatric Examination and Board Review (217 page)

13.
(B)
Penicillin does not cause type II or proximal RTA.

14.
(D)
All of the mentioned drugs except amoxicillin can cause type I or distal RTA.

15.
(E)
An HCO
₃
reabsorption defect occurs in type II or proximal RTA, whereas type I or distal RTA can be caused by a proton pump failure or back leak of excreted proton (hydrogen ion) into the cells of the cortical collecting duct. This back-leak phenomenon typically occurs in the RTA that occurs with amphotericin therapy.

16.
(A)
Type II or proximal RTA can result from an isolated defect in proximal tubular HCO
₃
⁻
absorption, or it can be caused by a bicarbonate reabsorption defect as a part of generalized proximal tubular disorder with aminoaciduria, glycosuria, and phosphaturia (seen in Fanconi syndrome).

17.
(E)
Type IV or hyperkalemic RTA can result from pseudohypoaldosteronism (because of insensitivity of renal tubular cells to aldosterone), as commonly seen in children, or as a result of aldosterone deficiency from various causes in children and adults. A common associated finding in adults with hyporeninemic hypoaldosteronism is seen in elderly diabetic patients as a result of hypofunction of the juxtaglomerular apparatus and consequent hyporeninemia and hypoaldosteronism. An example of hypoaldosteronism in children is congenital adrenal hyperplasia.

18.
(D)
In type IV RTA secondary to pseudohypoaldosteronism, there is insensitivity of the cortical collecting duct cells to aldosterone. Serum aldosterone levels are normal or high. Therefore mineralocorticoid therapy would not help. These patients are best treated with diuretics such as loop diuretics like furosemide and/or distal tubular diuretics like thiazides. These diuretics help improve hyperkalemia by delivering an excess of Na in the filtrate to the cortical collecting duct. This increased Na concentration in the urinary filtrate with a consequent increase in the Na gradient leads to K-Na exchange in the cortical collecting duct with consequent increased K excretion in the urine.

19.
(B)
Hyporeninemic hypoaldosteronism occurs in elderly diabetic patients as a result of the dysfunction of juxtaglomerular apparatus, and it is best treated with mineralocorticoids like fludrocortisone.

S
UGGESTED
R
EADING

Abelow B, ed.
Understanding Acid
-
Base.
Baltimore, MD: Williams and Wilkins; 1998.

Gennari FJ, ed.
Medical Management of Kidney and Electrolyte Disorders
. New York, NY: Marcel Dekker; 2001:201-202.

Herrin JT. Renal tubular acidosis. In: Anver ED, Harmon WE, Niaudet P, eds.
Pediatric Nephrology.
6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009.

CASE 124: A 7-YEAR-OLD WITH ENURESIS

A 7-year-old white girl has a history of bedwetting. According to Mom, her daughter was born by normal vaginal delivery at term and had an uneventful neonatal period. She was out of pull-ups during the day at 2 years of age. She currently wets the bed almost every night. However, she did have a 2-month period of dry nights with occasional wettings between 5 and 6 years of age. In the daytime, she tends to have urgency and frequency of micturition with occasional dribbling of urine on the way to the bathroom. She tends to have increased fluid intake on occasions. Mom has also noticed small round stains of urine on her underwear. There is no history of UTIs. The child’s school performance has been satisfactory. The family moved to Chicago 6 months ago, and there are no other recent significant events in the family. The family history is negative apart from a history of bedwetting in the father as a child.

Her physical examination, apart from palpable fecal masses in the left iliac fossa and suprapubic areas, is unremarkable. There is a sacral dimple with no hairy patch. Her deep tendon reflexes are normal, and there is no leg length discrepancy or wasting of muscles in either lower extremity.

The results of laboratory tests are as follows:

SELECT THE ONE BEST ANSWER

1.
This girl has enuresis by definition because

(A) daytime bladder control is usually achieved at 5 years of age and nighttime control at 6 years of age for a girl

(B) daytime bladder control is usually achieved at 2 years of age and nighttime control at 5 years of age for a girl

(C) daytime bladder control is usually achieved at 4 years of age and nighttime control at 8 years of age for a girl

(D) daytime bladder control is usually achieved at 6 years of age and nighttime control at 8 years of age for a girl

(E) daytime bladder control is usually achieved at 6 years of age and nighttime control at 2 years of age for a girl

2.
This girl most likely has which of the following?

(A) secondary daytime and nighttime enuresis and constipation

(B) primary nocturnal enuresis with daytime detrusor hyperactivity and constipation

(C) secondary nocturnal enuresis with daytime detrusor hyperactivity

(D) nephrogenic diabetes insipidus

(E) central diabetes insipidus

3.
The prevalence of this condition at this age is

(A) 6-9%

(B) 10-15%

(C) 25-30%

(D) 40%

(E) 1-5%

4.
The differential diagnosis of this condition in this girl includes all except

(A) new-onset diabetes mellitus

(B) obstructive sleep apnea

(C) UTI

(D) posterior urethral valves

(E) spina bifida occulta

5.
Further investigations that must be performed in this patient at this point include

(A) renal US

(B) VCUG

(C) urodynamic studies

(D) all of the above

(E) none of the above

6.
The risk of occurrence of enuresis in a child is

(A) 44% if one parent had the condition or 77% if both parents had the condition as a child

(B) 15% if one parent had the condition or 25% if both parents had the condition as a child

(C) 5% if one parent had the condition or 10% if both parents had the condition as a child

(D) 0% if one parent had the condition or 15% if both parents had the condition as a child

(E) 0% if one parent had the condition or 50% if both parents had the condition as a child

7.
Which of the following pharmacologic agents would most likely help this child’s symptoms?

(A) oxybutynin chloride

(B) imipramine

(C) tolterodine tartrate

(D) A and C only

(E) none of the above

8.
All of the following nonpharmacologic methods can also be tried in this child except

(A) fluid restriction in the evenings

(B) regular punishment for every wet night

(C) enuresis alarm program

(D) voiding before bedtime

(E) acknowledging to the child that parents understand that bedwetting is not being done intentionally (demystification)

9.
The most effective treatment for primary nocturnal enuresis with a pure arousal mechanism problem or monosymptomatic nocturnal enuresis is

(A) intranasal or oral DDAVP

(B) imipramine

(C) acupuncture

(D) an enuresis alarm program

(E) chiropractic manipulation

10.
Primary nocturnal enuresis can be associated with

(A) abnormal arousal-from-sleep mechanism

(B) nighttime wetting with daytime detrusor hyperactivity or uninhibited bladder contractions

(C) nighttime polyuria

(D) A and B only

(E) all of the above

11.
Nocturnal enuresis can be inherited as an