Clinical diagnosis
Case 100
【Progress】We were really embarrassing to diagnose this case because of absence of the determinant findings. However, she mentioned us to get antibiotics before visiting us. We considered that was why urine test revealed no abnormality.
She was given both medicines of anticoagulants and antibiotics, leading to speedy recovery from abdominal pain and fever.
【Discussion】
The problems in this case were the isolation of the medical findings. She routinely got contraceptive pill which is known to cause thrombophlebitis as a complication event. Contrast-enhanced CT showed bilateral decreased enhanced (low density) areas in both kidneys: especially marked wedge-typed low density area in the left kidney, indicative of renal infarction or acute focal bacterial nephritis. However, urine test revealed no evidence of hematuria and white blood cells. Laboratory blood test revealed no elevation of LDH which is very sensitive to respond to renal infarction.
The greater dosage of contraceptive pill is known to increase the risk of thrombophlebitis (1). The incidence of thrombophlebitis in Japanese women is reported to be much less than western women, probably because of Japanese women being more agile (1). Thrombophlebitis usually occurs in the lower legs, risky to pulmonary embolism. Thrombophlebitis can occur in renal vein, causing infarction due to renal vein thrombophlebitis, but it rarely occurs. Further, all reported cases had macroscopic emboli in the main renal vein on imaging modalities such as enhanced CT and/or angiography.(1). In our case, enhanced CT showed no thrombus of right and left renal veins, although the occlusions of small branch veins could not be deniable.
In the literature, the elevation of LDH (lactic dehydrogenase) value occurs in renal infarction with the incidence of approximately 90% or greater (1). The enzyme of LDH exists in most living cells throughout the body and catalyze to convert pyruvic acid to lactate in the less oxygen condition back (2). LDH elevation clinically occurs in cardiac infarction, renal infarction and malignant lymphoma. In our case, the value of LDH was 157/U (124 - 222), indicative of renal infarction being considered to be negative although enhanced CT showed wedge-typed low density in the left kidney.
Further, cortical rim sign was negative in enhance CT in our case. Non-enhanced CT is often useless to differentiate between renal infarction and acute focal bacterial nephritis. Contrast-enhanced CT sometimes shows cortical rim sign in cases with renal infarction. The renal cortical rim can get blood supply from a renal capsular artery which is an early branch of the renal artery and then, occlusion of the segmental renal artery spares ischemic infarction in the renal rim (4). Meanwhile, pyelonephritis progress from pelvis to renal capsule or extra renal space via renal parenchyma, indicative of no sparing renal rim. Then, renal rim sign is useful to differentiate renal infarction from acute focal nephritis, although this sign is seen in approximately half of renal infarctions (5 – 8). Our case with enhanced CT did not have cortical rim sign.
Acute focal bacterial nephritis previously known as acute focal lobar nephronia is a middle level-disorder between microscopic pyelonephritis and renal abscess. The typical images of acute focal bacterial nephritis are wedge-shaped renal parenchyma with decreased enhancement. Enhanced CT images of our case matched to this finding, wedge-typed low density without cortical rim sign in bilateral kidneys.
【Summary】
We present a thirty-year-old female presented suffering from abdominal pain, and high fever. Laboratory test revealed white blood cells 23260/mm3, neutrophils 85%, CRP 23.26 mg/dL, LDH 157 U/L, D dimer 1.4 (< 1 microgram/mL) and urine test depicted negative red blood cells and negative white blood cells. Contrast-enhanced CT showed decreased enhanced areas in both kidneys including a wedged-type low density without cortical rim sign in the left kidney. She was diagnosed finally as acute focal bacterial nephritis based on the ingestion of antibiotics before presenting in our hospital and the normal level of LDH. We should keep in mind that LDH level increases in case of acute renal infarction and CT shows no cortical rim sign in cases with acute focal bacterial nephritis. Cortical rim sign is a characteristic finding of renal infarction, although it is found in approximately a half of renal infarctions.
【References】
1.Sasaki Y, et al. Renal vein thrombosis associated with oral contraception and smoking: a case report from Japan, with literature review. CEN Case Rep. 2014 May; 3(1): 100–105. Published online 2013 Sep 4. doi: 10.1007/s13730-013-0095-9
2.“Peroxisomal lactate dehydrogenase is generated by translational readthrough in mammals”. eLife 3: e03640. (2014). doi:10.7554/eLife.03640. PMC 4359377. PMID 25247702
3.Dyer RB, et al. Classic signs in uroradiology. Radiographics. 2004; 24: S247-80. Radiographics (full text) - doi:10.1148/rg.24si045509
4.Chu PL, et al. Clinical characteristics of patients with segmental renal infarction. Nephrology (Carlton) 2006;11(4):336–340
5.Tatsuji Maeshiro, et al. Acute focal bacterial nephritis. BMJ Case Rep. 2014; bcr2014205199. Published online 2014 Jun 3. doi: 10.1136/bcr-2014-205199 PMCID: PMC4054329
6.Rosenfield AT, et al. Acute focal bacterial nephritis (acute lobar nephronia). Radiology 1979;132:553–61 [PubMed]
7.Shimizu M, et al. Evolution of acute focal bacterial nephritis into a renal abscess. Pediatr Nephrol 2005;20:93–5 [PubMed]
8.Soulen MC, et al. Bacterial renal infection: role of CT. Radiology 1989;171:703–707
2018.4.11