An extremely rare cause of flank pain: Answers

Wha t is your most likely diagnosis?

The multifocal bilateral wedge-shaped image (triangular defects in the renal parenchyma) is typical for renal infarction and allowed us to diagnose the patient with renal infarction. In addition to the wedge-shaped image, the presence of nausea/vomiting, flank pain, high C-reactive protein, and D-dimer values also indicate acute kidney infarction.

Although renal infarction can be idiopathic, it is often secondary to an underlying disease [1]. Embolism secondary to cardiac disease is among the leading causes in the adult age group [2, 3]. Trauma, spontaneous renal artery dissection, fibromuscular dysplasia, and thrombotic aneurysms of the renal artery are the causes of renal infarction secondary to renal artery injury [1]. In addition to diseases that may predispose to hypercoagulable conditions, such as hereditary thrombophilic diseases and nephrotic syndrome, renal infarction has also been reported in the course of rheumatological diseases such as systemic lupus erythematosus (SLE), primary antiphospholipid syndrome, polyarteritis nodosa, mixed connective tissue disease, Henoch–Schönlein vasculitis, and Behcet disease [3‐5]. Finally, with the COVID-19 pandemic, cases of thrombotic microangiopathy and renal infarction with/without arterial thrombus in the renal vasculature have also been described [6].

First, cardioembolic origin, which is the most common cause in etiology, must be ruled out [2]. This healthy-looking 12-year-old patient had no known heart disease. A normal 2D echocardiogram and electrocardiography of the patient excluded possible embolism secondary to cardiac diseases. Renal injury is also one of the common causes of renal infarction along with cardiac causes [1]. The patient had no history of trauma. Angiographic imaging of the arterial tree was performed to exclude the presence of renal injury secondary to diseases such as aneurisms or dissections. Computerized tomography (CT) angiography revealed no thrombus in the abdominal aorta and its branches, as well as in the renal arteries. There was no family history of bleeding or coagulation disorders, and the coagulation profile was normal. However, due to the presence of prothrombotic factors in the etiology of renal infarction, thrombosis tests (Factor V, Antithrombin III, protein C, and S deficiency) were studied to exclude hypercoagulable states [3, 5]. Hemoglobin electrophoresis studied in the differential diagnosis of sickle cell anemia was normal. Complement levels (serum C3 1.2 g/l, serum C4 0.3 g/l) were in normal range. Antiphospholipid and anticardiolipin IgM and IgG antibody titers were negative. Negative ANA (anti-nuclear antibody) and the ENA (extractable nuclear antigen) panel led us to exclude rheumatological diseases such as SLE and mixed connective tissue disease [3, 5].

The patient’s history revealed that he and his family members had fever and cough for 3 weeks, but were not tested. COVID-19 PCR and antibodies were sent due to the conjunctival hyperemia of the patient with high fever before hospitalization, as well as lymphopenia and an increase in liver enzymes. Tests were negative for COVID-19 infection on reverse transcription-polymerase chain reaction (PCR) of nasal swab and positive for IgG and IgM antibodies. Renal infarction due to acute COVID-19-associated coagulopathy (CAC) was considered with the present findings in the patient. However, we could not rule out the suspicion of multisystem inflammatory syndrome in children (MIS-C), according to the World Health Organization (WHO) criteria in the patient with the presence of positive serology and laboratory findings accompanied by non-purulent bilateral conjunctivitis developed 3 weeks after the acute infection [7].

Intravenous antibiotic treatment was initiated in an external center with the suspicion of acute pyelonephritis empirically. Low molecular weight heparin (LMWH) 100 U/dose per kg was added with the diagnosis of acute renal infarction as an anticoagulant therapy. Although renal infarction due to CAC was considered, intravenous immunoglobulin (1 g/kg) therapy and methylprednisolone (2 mg/kg) were given because of ongoing fever and the diagnosis of atypical MIS-C could not be excluded. Echocardiogram revealed patent foramen ovale. The patient, whose fever regressed, lymphopenia and kidney functions improved, and proteinuria resolved (urine beta 2 microglobulin (0.21 mg/l)), was discharged on the 10th day of hospitalization. Since no signs of renal infarction were found in the abdominal CT performed in the first month of treatment, LMWH treatment was discontinued, and the patient was commenced on 3 months of acetylsalicylic acid therapy.