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Saudi Journal of Kidney Diseases and Transplantation
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Table of Contents   
CASE REPORT  
Year : 2018  |  Volume : 29  |  Issue : 5  |  Page : 1240-1244
Distal renal tubular acidosis secondary to vesico-ureteric reflux: A case report with review of literature


1 Department of Pediatrics, Medanta Super-Speciality Hospital, Indore, Madhya Pradesh, India
2 Department of Endocrinology, Medanta Super-Speciality Hospital, Indore, Madhya Pradesh, India
3 Bombay Hospital and Research Center, Indore, Madhya Pradesh, India

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Date of Submission10-Jan-2018
Date of Acceptance20-Feb-2018
Date of Web Publication26-Oct-2018
 

   Abstract 

Vesicoureteric reflux (VUR) is the most common congenital anomaly of the urinary tract that occurs in 30%–50% of children presenting with recurrent urinary tract infections. Long-standing untreated VUR results in renal scarring and hydronephrotic changes ultimately leading to chronic renal failure and arterial hypertension. However, it may also result in diffuse tubulopathy compromising the concentrating capacity of tubules and urinary acidification defects. Renal tubular dysfunction should be considered in all children with VUR presenting with failure to thrive, rickets, bony deformity/pain, hypokalemia, and metabolic acidosis. We report such a case of a 16-year-old male adolescent who presented with rickets, failure to gain weight and height, bony pains, and muscle weakness with a history of VUR. On investigation, he was found to have normal anion gap metabolic acidosis with hypokalemia suggestive of distal renal tubular acidosis. He responded well to oral alkali and potassium replacement therapy.

How to cite this article:
Bharani A, Bharani T, Bharani R. Distal renal tubular acidosis secondary to vesico-ureteric reflux: A case report with review of literature. Saudi J Kidney Dis Transpl 2018;29:1240-4

How to cite this URL:
Bharani A, Bharani T, Bharani R. Distal renal tubular acidosis secondary to vesico-ureteric reflux: A case report with review of literature. Saudi J Kidney Dis Transpl [serial online] 2018 [cited 2018 Nov 15];29:1240-4. Available from: http://www.sjkdt.org/text.asp?2018/29/5/1240/243943

   Introduction Top


The renal tubules play an important role in fluid, electrolyte, and acid-base homeostasis. In 1946, Albright et al described distal renal tubular acidosis (dRTA) as a distinct clinical entity.[1] dRTA is a nonuremic defect of urinary acidification characterized by normal anion gap hyperchloremic metabolic acidosis. It is characterized by an inability to lower urinary pH <5.5 even in the face of systemic acidosis and nephrocalcinosis. These patients have features of rickets/osteomalacia and stunted growth. It may be primary, due to various genetic mutations or secondary to systemic causes such as Sjogren’s syndrome, lupus, sickle cell disease, or vesicoureteric reflux (VUR)/obstructive uropathy.

VUR is the retrograde flow of urine from the bladder into the ureter and is the most frequent malformation of the urinary tract. It occurs in 30%–50% of children with recurrent urinary infections.[2] It predisposes the kidney to parenchymal infection, resultant scarring and hydronephrotic changes by allowing ascent of bacteria from bladder to the upper urinary tract.

Reflux nephropathy develops in 30%–60% of children with VUR. It predominates in girls at a proportion of 4:1, but its severity is greater in boys.[3] The most serious consequences are chronic renal failure and arterial hypertension.[4] Long-standing VUR can also lead to diffuse tubulopathy and urinary acidification defects.[5] Very few cases of dRTA secondary to VUR have been reported in the literature. We report such a rare case of dRTA secondary to VUR in a 16-year-old male adolescent.


   Case Report Top


A 16-year-old male adolescent born of a nonconsanguineous marriage presented to us with complaints of failure to gain weight, bony pains, and muscle weakness for the last three years. He had a significant history. He was symptomatic since the age of three years when he had recurrent urinary tract infections, poor feeding, and poor growth. On work-up, he was found to have Grade 4 VUR [Figure 1], [Figure 2], [Figure 3] for which he was operated. Post-operatively, the reflux got corrected, but the hydronephrosis persisted, however, he was not symptomatic.
Figure 1: Micturating cystourethrogram at diagnosis of vesico-ureteric reflux showing grade 4 reflux and hydronephrosis.

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Figure 2: Ultrasonography at diagnosis showing severe hydronephrotic changes in the kidney.

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Figure 3: Ultrasonography at diagnosis showing bilaterally dilated, tortuous ureters.

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He was first by birth order and his younger sister (12 years) was asymptomatic. On examination, he was found to have height: 145 cm (<2SD), weight: 45 kg, pulse rate: 86/min, blood pressure: 110/70 mm Hg, SMR = tanner’s stage 4, signs of rickets in the form of wrist widening, waddling gait. On systemic examination, proximal muscle weakness was present. On investigations [Table 1], he was found to have hyperchloremic, normal anion gap, metabolic acidosis with raised intact parathormone, and alkaline phosphatase. Simultaneous urinary pH was 6.5 despite systemic acidosis. Serum creatinine was normal. X-ray of bilateral wrists showed widening and fraying of metaphysis [Figure 4].
Table 1: Biochemical investigations of the patient.

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Figure 4: X ray bilateral hand at presentation showing showing metaphyseal widening and fraying.

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With these investigations, a diagnosis of distal renal tubular acidosis was made secondary to reflux nephropathy. He was started on alkali replacement in the form of sodium bicarbonate tablets, oral potassium supplements, oral calcium and Vitamin D. With this treatment, his bone pains decreased and muscle weakness improved. His alkaline phosphatase normalized, iPTH nearly normalized and acidosis got corrected. Moreover, his X-ray findings improved [Figure 5].
Figure 5: X-ray of the left hand before and 3 months into therapy, showing significant correction of rachitic deformity.

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   Discussion Top


Considering the spectrum of tubular functions, these disorders result in varied manifestations emphasizing the need for their consideration in several clinical conditions.[6] Nonspecific features mandate the need for high index of suspicion for these disorders.[7]

Distal renal tubular acidosis is characterized by decreased proton excretion due to a proton pump defect or back diffusion of protons. Tubular dysfunction should be considered in all children with failure to thrive, polyuria, refractory rickets, hypokalemia, and metabolic acidosis.

Renal tubular acidosis and diarrhea are important causes of metabolic acidosis in children. These disorders can be readily differentiated from most other causes of metabolic acidosis by estimation of the plasma anion gap. Normal anion gap in the presence of acidosis (hyperchloremic metabolic acidosis) suggests increased urinary (proximal RTA) or gastrointestinal loss (diarrhea) of bicarbonate or impaired excretion of H+ ions (dRTA).[8] Hypokalemia is usually associated with metabolic alkalosis. The occurrence of metabolic acidosis and hypokalemia suggests RTA or gastrointestinal loss of bicarbonate (diarrhea, ureterosigmoidostomy).

In children, dRTA is almost always observed as a primary entity and rarely associated with autoimmune conditions (Sjogren’s syndrome, lupus). Pathogenically, dRTA can develop when there is a true failure of the distal nephron to secrete (secretory defect or classic dRTA) or when such capacity is intrinsically intact, but secondarily impaired. The non-secretory defects are caused by either an inability to create a steep lumen-to-cell H+ gradient due to increased back leak of secreted H+ (gradient defect) or an inability to generate/maintain a distal lumen-negative transepithelial difference (voltage-dependent defect), as observed in patients with impaired distal Na+ transport (obstructive uropathy, sickle cell disease).[9]

Investigations in children with distal (type 1) RTA include estimation of urine calcium excretion, ultrasound for renal calcification and work-up for secondary causes (e.g., obstructive uropathy, reflux nephropathy, and chronic tubulointerstitial nephritis).

Treatment of RTA includes administration of alkali in the form of sodium bicarbonate 7.5% (1 mEq/mL) or tablets; Shohl solution (1 mEq/ mL); Polycitra solution (2 mEq/L). Alkali therapy is usually combined with potassium replacement to avoid severe hypokalemia. Potassium supplements in patients with acidosis are usually administered as citrate salts.

Although chronic renal failure and arterial hypertension are considered as the most important complications of VUR, urinary concentration and distal acidification defects are also important complications that may be seen in some children which should also be ruled out. The acidemia decreases bone collagen synthesis and determines end-organ resistance to growth hormone and IGF-1.[10] This results in growth failure. If not timely treated with alkali replacement and potassium therapy, it results in varied symptoms of poor growth, muscle weakness, and bony pains. Hence, the physician should be aware of the clinical presentation and the correct management of this illness to prevent rickets/osteomalacia and growth retardation in patients with long-standing VUR.

Conflict of interest: None declared.

 
   References Top

1.
Albright F, Burnett CH. Osteomalacia and late rickets; the various etiologies met in the United States with emphasis on that resulting from a specific form of renal acidosis, the therapeutic indications for each etiological sub-group, and the relationship between osteomalacia and Milkman’s syndrome. Medicine (Baltimore) 1946;25:399-479.  Back to cited text no. 1
    
2.
Hodson J. Reflux nephropathy. Med Clin North Am 1978;62:1201.  Back to cited text no. 2
    
3.
Goldraich NP, Goldraich IH. Followup of conservatively treated children with high and low grade vesicoureteral reflux: A prospective study. J Urol 1992;148:1688-92.  Back to cited text no. 3
    
4.
Broyer M, Rizzoni G, Brunner FP. Combined report on regular dialysis and transplantation of children in Europe. Proc Eur Dial Transplant Assoc 1989;22:55.  Back to cited text no. 4
    
5.
Miyazaki Y, Ichikawa I. Ontogeny of congenital anomalies of the kidney and urinary tract, CAKUT. Pediatr Int 2003;45:598-604.  Back to cited text no. 5
    
6.
Rodriguez-Soriano J. Tubular disorders of electrolyte regulation. In: Avner ED, Harmon WE, Niaudet P, editors. Pediatric Nephrology. 5th ed. Baltimore: Lippincot Williams & Wilkins; 2004. p. 729-56.  Back to cited text no. 6
    
7.
Van’t Hoff W. Renal tubular disorders. In: Webb NJ, Postlethwaite RJ, editors. Clinical Pediatric Nephrology. 3rd ed. New York: Oxford Press; 2003. p. 103-12.  Back to cited text no. 7
    
8.
Postlethwaite RJ. The approach to a child with metabolic acidosis or alkalosis. In: Webb NJ, Postlethwaite RJ, editors. Clinical Pediatric Nephrology. 3rd ed. New York: Oxford Press; 2003. p. 61-72.  Back to cited text no. 8
    
9.
Rodríguez Soriano J. Renal tubular acidosis: The clinical entity. J Am Soc Nephrol 2002; 13:2160-70.  Back to cited text no. 9
    
10.
Guizar JM, Kornhauser C, Malacara JM, Sanchez G, Zamora J. Renal tubular acidosis in children with vesicoureteral reflux. J Urol 1996;156:193-5.  Back to cited text no. 10
    

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Correspondence Address:
Dr. Anjali Bharani
Department of Pediatrics, Medanta Super-Speciality Hospital, Indore, Madhya Pradesh
India
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DOI: 10.4103/1319-2442.243943

PMID: 30381529

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    Figures

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