Hemorrhagic fever with renal syndrome: MR imaging of the kidney

A case of ruptured renal cortical arteriovenous malformation of the right testicular vein in hemorrhagic fever with renal syndrome

Hemorrhagic fever with renal syndrome (HFRS) is an acute viral disease characterized by fever, hemorrhage, and renal failure. Among the various hemorrhagic complications of HFRS, the spontaneous rupture of an arteriovenous malformation of the testicular vessels with a retroperitoneal hematoma is a rare finding. Here, we report a case of HFRS complicated by a massive retroperitoneal hematoma that was treated with transcatheter arterial embolization.

Renal artery embolization of perirenal hematoma in hemorrhagic fever with renal syndrome: a case report

Hemorrhagic fever with renal syndrome (HFRS) is an acute viral disease characterized by fever, hemorrhage and renal failure. Among the various hemorrhagic complications of HFRS, spontaneous rupture of the kidney and perirenal hematoma are very rare findings. We report here on a case of HFRS complicated by massive perirenal hematoma, and this was treated with transcatheter arterial embolization.

Magnetic resonance renography findings and their clinical associations in nephropathia epidemica

PURPOSE

To evaluate, with magnetic resonance renography (MRR), the dynamics of renal function in patients with nephropathia epidemica (NE) and to correlate the findings with the clinical course of NE.

MATERIAL AND METHODS

MRR was performed on 20 hospitalized NE patients during the acute phase of the disease. A repeat MRR study was done 5-8 months later. Primary and repeat MRR studies were compared and functional findings evaluated.

RESULTS

The uptake slope of the contrast enhancement curve was abnormal in the primary study in 14 patients, maximum level of enhancement in 11, decreasing slope of contrast enhancement curve in 14, and signal drop at time in 10 patients when the primary and repeat studies were compared. The greater change in the uptake slope of contrast enhancement, maximum level of enhancement, decreasing slope of enhancement, and signal drop at time between primary and repeat MRR studies evinced a mild association with the severity of clinical renal insufficiency and fluid volume overload.

CONCLUSION

Measurable functional MRR findings were recorded in 14/20 NE patients. The severity of the findings was mildly associated with the degree of clinical renal insufficiency and fluid volume overload.

Renal MRI findings and their clinical associations in nephropathia epidemica: analysis of quantitative findings

Morphologic renal magnetic resonance imaging (MRI) findings in patients with nephropathia epidemica (NE) were evaluated, and these findings were correlated with the clinical course of NE. Renal MRI was performed in 20 hospitalized NE patients during the acute phase of their disease. A repeat MRI study was made 5-8 months later. Renal parenchymal volume, renal length and parenchymal thickness were decreased in all patients in the repeat study. Edema/fluid collections were found bilaterally in 16 patients in the primary MRI study. Greater change in parenchymal volume, renal length and parenchymal thickness between the primary and the repeat MRI study as well as the presence of edema/fluid collections in the primary study evinced mild association with clinical fluid volume overload, high blood pressure level, inflammation, thrombocytopenia and severe clinical renal insufficiency. Change in parenchymal volume was associated with a severe clinical course more markedly than the other MRI findings. Measurable renal MRI changes occurred in every NE patient. The severity of the findings in MRI evinced mild association with clinical fluid volume overload, high blood pressure level, inflammation, thrombocytopenia and severe clinical renal insufficiency. Based on this study and our previous ultrasound (US) findings, we prefer US as the primary examination mode in NE patients.

MR imaging in abdominal emergencies

The use of MR imaging in the emergency setting is evolving. Clear indications include situations in need of contrast media when iodinated contrast cannot be administered or to facilitate assessments in pregnant patients and children when exposure to ionizing radiation is considered unacceptable. The availability of rapid, motion-immune sequences now makes MR imaging a feasible study in less cooperative patients extending the range of patients for whom a diagnostic study can be achieved. Capitalizing on the unique benefits of MR imaging there is optimism that MR imaging can eliminate test redundancy and impact patient care in a cost-effective manner. Further investigations are needed to identify the diagnostic algorithms for which this favorable use holds true.

Atypical low-signal-intensity renal parenchyma: causes and patterns

Certain renal diseases manifest as low signal intensity of the renal parenchyma on magnetic resonance images. Sometimes, the appearance is sufficiently characteristic to allow a specific radiologic diagnosis to be made. The causes of this finding can be classified into three main categories on the basis of the pathophysiology: hemolysis, infection, and vascular disease. The first category includes paroxysmal nocturnal hemoglobinuria (PNH), hemosiderin deposition in the renal cortex from mechanical hemolysis, and sickle cell disease. The second category includes hemorrhagic fever with renal syndrome (HFRS). The third category includes acute renal vein thrombosis, renal cortical necrosis, renal arterial infarction, rejection of a transplanted kidney, and acute nonmyoglobinuric renal failure with severe loin pain and patchy renal vasoconstriction. These disease processes have different patterns of low signal intensity. PNH, hemosiderin deposition from mechanical hemolysis, and sickle cell disease involve the entire cortex including the columns of Bertin. HFRS involves the medulla, especially the outer medulla, whereas cortical necrosis involves the inner cortex including the columns of Bertin. In renal vein thrombosis, low-signal-intensity lesions involve the outer medulla, an appearance resembling that of HFRS. Wedge-shaped low-signal-intensity regions involving both the cortex and the medulla are seen in arterial infarction.

MR findings of renal cortical necrosis

PURPOSE

Evaluating the MR findings of renal cortical necrosis was the purpose of this study.

METHOD

Eight series of T1-/T2-weighted (n = 8) and contrast-enhanced T1-weighted (n = 4) MR images in six patients with renal cortical necrosis diagnosed by renal biopsy (n = 4) or on clinical grounds (n = 2) were reviewed. In those who had follow-up MRI (n = 2) or comparable CT (n = 3), interval changes of MR findings and comparison with CT images were done.

RESULTS

Swollen kidney with dark signal intensity rim involving the inner cortex and column of Bertin was noted on T2-and T1-weighted images. It was more conspicuous on T2-weighted images. The lesion did not enhance and was differentiated from uninvolved renal parenchyma. In the follow-up MRI, thickened dark signal intensity was more prominent and proved to be calcification or fibrosis.

CONCLUSION

MRI, especially T2-weighted and contrast-enhanced T1-weighted imaging, was helpful in evaluating renal cortical necrosis.

Functional assessment of canine kidneys after acute vascular occlusion on Gd-DTPA-enhanced dynamic echo-planar MR imaging

RATIONALE AND OBJECTIVES

To assess the alteration in renal transit of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) in dog kidneys after acute vascular occlusion on dynamic echo-planar imaging (EPI).

METHODS

Dynamic 240-ms EPI series (repetition time/echo time/inversion time [TR/TE/TI] = 3000/42.1/100 ms) of the midcoronal plane of both kidneys of dogs anesthetized by intravenous administration of phenobarbital sodium and ketamine hydrochloride were obtained before and after ligation of the left renal vein (n = 6) or artery (n = 6) for 40 minutes after a 2-second-rate bolus injection of a 0.05 mmol/kg dose of Gd-DTPA. Renal Gd-DTPA transit was analyzed on the time-DeltaR2* curves in each layer of the outer cortex (OC), juxtamedullary cortex and outer zone of the medulla (JMC-OM), and the inner zone of the medulla (IM). The results were compared with those in six normal animals and those of a fast gradient-echo T1-weighted dynamic study performed in other vein- (n = 6) or artery- (n = 6) occluded animals and six normal animals. The histopathological basis of the altered Gd-DTPA transit was also evaluated.

RESULTS

The dynamic EPI showed rapid Gd-DTPA transit through each of the five concentric layers, with three separate peaks on the time-DeltaR2* curves. The vein-occluded kidneys showed immediate swelling, with a significant increase in the cross-sectional area proportion of the JMC-OM layer compared with normals (32% +/- 2% vs 24% +/- 2%, P < 0.0001) and intensely congested capillaries, tubular, obliterated material, and gradual and persistent enhancement of the OC and JMC-OM layers but poor Gd-DTPA migration to the IM layer. The artery-occluded kidneys showed a significant reduction in the entire cross-sectional area compared with normals (1352 +/- 69 vs 1432 +/- 47 mm(2), P < 0.05) and poor enhancement, with significant decreases in the area under the time-DeltaR2* curve of the OC and JMC-OM layers compared with the vein-occluded kidneys (79 +/- 50 vs 324 +/- 108 and 82 +/- 42 vs 326 +/- 113, respectively; both P < 0.0001), despite minimal histological damage. In both models, the nonaffected kidneys showed significant increases in the area under the time-DeltaR2* curves compared with baseline. The time course of vascular and tubular Gd-DTPA transit was more detailed by the EPI study than by the T1-weighted imaging study.

CONCLUSIONS

Echo-planar imaging has an excellent ability to follow the rapid, renal Gd-DTPA transit through the regional anatomy of the canine kidney. After venous occlusion, the JMC-OM layer may be the most affected site, primarily causing renal swelling and interruption of tubular Gd-DTPA transit and concentration. In contrast, an initial block of vascular Gd-DTPA inflow is the primary effect of arterial occlusion. Nonaffected kidneys seem to compensate by increasing excretion of Gd-DTPA.

Pathogenetic and clinical aspects of the renal involvement in hemorrhagic fever with renal syndrome

Hemorrhagic fever with renal syndrome is the most common clinical manifestation of hantavirus infection. The main target organ is the kidney, resulting in an interstitial hemorrhagic nephritis and sometimes acute tubular necrosis. The pathogenesis is still largely unknown, but several recent studies indicate an important role for immune mechanisms including increased expression of cytokines, for example, tumor necrosis factor. Immunohistochemical studies of kidney biopsies have revealed deposits of IgG, IgM, and C3, but deposits were significantly less numerous than in chronic immune complex disease. Since hantaviruses are not cytolytic, a direct detrimental effect of the infecting virus is less likely. The long-term prognosis of hemorrhagic fever with renal syndrome seems to be favorable, but there are reports that previous hantavirus infection is associated with an increased risk of hypertensive renal disease. Prospective longitudinal studies addressing this issue are underway.

MR of the kidneys, liver, and spleen in paroxysmal nocturnal hemoglobinuria

The magnetic resonance (MR) findings in the liver, kidneys, and spleen in eight patients with paroxysmal nocturnal hemoglobinuria (PNH) were retrospectively reviewed to determine whether characteristic features could be demonstrated. Eight patients underwent abdominal MR examinations by gradient echo sequences (seven patients), spin-echo sequences (seven patients), and inversion recovery (one patient). Signal intensities of the kidneys, liver, and spleen were visually evaluated. Autopsy and liver biopsy correlation were available in one case each. Renal signal intensity was decreased in all eight patients by either gradient-echo or T2-weighted sequences and in the single inversion recovery sequence. Hepatic signal intensity was decreased in three of eight patients on spin- and gradient-echo images. Splenic signal intensity was decreased in three of eight patients on spin- and gradient-echo images, and in two of these was manifest as focal low signal spots (Gamna-Gandy bodies). While the signal intensity in the renal cortex is typically decreased in patients with PNH, signal intensities in the liver and spleen are variable. Low signal intensity in the kidneys is due to hemosiderin deposition resulting from intravascular hemolysis, whereas low signal intensity in the liver or spleen may be due to either transfusion siderosis, or as a consequence of hepatic or portal venous thrombosis.