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Case 371


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The patient is a 33-year-old male, with a previous history of multiple renal calculi since childhood, with spontaneous and surgical passing. He was admitted for a new surgical procedure, when medical evaluation was requested, revealing hypocalcemia, hypophosphatemia and metabolic acidosis. He denied having used prescription or recreational drugs. A plain abdominal radiograph was performed, in supine position, anteroposterior projection (images 1 and 2).

Given the medical history and images presented, what is the most prominent abnormality in this patient’s renal parenchyma?

a) Nephrolithiasis


b) Renal scar


c) Nephrocalcinosis


d) Polycystic kidneys


Image analysis


Image 1 – Plain abdominal radiograph, in supine position, anteroposterior projection. Multiple calcifications (highlighted by the green line) are seen grouped in the renal topography; the kidneys measure approximately 10 x 4 cm in the longitudinal and transverse axes, respectively. 



Image 2 – Plain abdominal radiograph, in supine position, anteroposterior projection (negative image). Multiple calcifications (highlighted by the green line) are seen grouped in the renal topography.



-RTA is a result of malfunctioning of the renal tubules responsible for HCO³- reabsorption (proximal RTA) or H+ excretion (distal RTA);

-RTA should be suspected in the presence of a hyperchloremic metabolic acidosis, with a normal anion gap;

-Urinary pH greater than 5.5 in patients with a normal anion gap is characteristic of distal RTA;

-When treating distal RTA, the goal is not only to correct biochemical abnormalities, but also to prevent progression of nephrocalcinosis and prevent chronic renal failure;

-In RTA, the prognosis is directly related to early diagnosis.



- Cheidde L, Ajzen SA, Tamer Langen CH, et al. A critical appraisal of the radiological evaluation of nephrocalcinosis. Nephron Clin Pract 2007; 106:c119.

- Piccoli GB, De Pascale A, Randone O, et al. Revisiting nephrocalcinosis: A single-centre perspective. A northern Italian experience. Nephrology (Carlton) 2016; 21:97.

- Blanchard A, Bockenhauer D, Bolignano D, et al. Gitelman syndrome: consensus and guidance from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference. Kidney Int 2017; 91:24.

- Schepens D, Verswijvel G, Kuypers D, Vanrenterghem Y. Images in Nephrology. Renal cortical nephrocalcinosis. Nephrol Dial Transplant 2000; 15:1080.

- Wrong O. Nephrocalcinosis. In: Oxford Textbook of Clinical Nephrology, Davison AM, Cameron JS, Grünfeld J, et al (Eds), Oxford University Press, Oxford 2005. p.1375.

- Soriano, JR. Renal Tubular Acidosis: The Clinical Entity. JASN Aug 2002, 13 (8) 2160-2170;



Luiz Gustavo de Faria Ferreira, 5th year medical student at UFMG.

Mail: gustavoff96[at]



Dr. Lilian Pires de Freitas do Carmo, nephrologist and assistant professor at the Faculdade de Medicina at UFMG.

Mail: lilianpfreitas[at]


Dr. Cécil Bruno Buldrini Filogônio, professor at the Department of Anatomy and Imaging at UFMG.

Mail: cecilbruno[at]



Gabriella Shiomatsu, Felipe Eduardo Fagundes Lopes, Larissa Rezende, Maria Cecília Nassif, professor José Nelson Mendes Vieira.


Translated by

Rafael Antonio Teixeira Malta, 6th year medical student at UFMG

Mail: rafaelmalta148[at]

Test question

(Municipal Health Secretary – Piracicaba, São Paulo)

Metabolic acidosis is the excess of acidity in the blood, characterized by an abnormally low bicarbonate concentration. In the clinical evaluation of acid-base disorders, the differential diagnosis can be obtained by calculating the anion gap. Which of the disorders below can cause a normal anion gap metabolic acidosis?

a) Distal (type 1) renal tubular acidosis


b) Ethylene glycol poisoning


c) Typical diabetic ketoacidosis


d) Salicylate poisoning





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