Acute renal infarction due to renal fibromuscular dyplasia: a case of mistaken identity

RK Patel1, MC Brown1,  M Seywright2, K Qureshi3 CC Geddes1

 1 Renal Unit, Western Infirmary, Dumbarton Road, Glasgow, UK

2 Pathology Dept., Western Infirmary, Dumbarton Road, Glasgow, UK

3 Urology Dept., Gartnavel General Hospital, Great Western Road, Glasgow, UK

Author for correspondence: Dr Colin Geddes, Consultant Nephrologist, Western Infirmary, Dumbarton Road, Glasgow G11 6NT U.K.

Email:  colin.geddes@northglasgow.scot.nhs.uk

SMJ 2008 53(2): 65

 

Abstract

A 53 year old male presented with right sided loin pain in the absence of other distinguishing symptoms, past medical history or examination findings. Investigation, a week later, revealed a right sided renal mass. He underwent laparascopic nephrectomy for presumed renal malignancy.  Surprisingly, the mass was an area of infarction and the renal artery had intimal-type fibromuscular dysplasia (FMD). This case demonstrates three important points. Firstly, renal infarction is a cause of acute loin pain. Secondly, delayed investigation can alter the radiological appearance of renal infarction.    Lastly, FMD is a rare condition, particularly in men, and can cause renal infarction.

 

Case History

We present a case that illustrates the importance of prompt investigation and keeping an open mind when approaching a patient with acute loin pain.

 

A 53 year old male developed acute, severe, fluctuating right-sided loin pain that resolved spontaneously over several hours. There were no associated urinary or gastrointestinal symptoms. He attended his general practitioner 6 hours later and was referred to urology for investigation. Past medical history included chronic back pain, for which he occasionally took non-steroidal anti–inflammatory drugs, and hypercholesterolaemia, treated with 20mg pravastatin daily. He was a smoker with no known allergies. Family history and systemic enquiry were unremarkable. His blood pressure was 170/80mmHg at presentation with a normal physical examination and urinalysis. Serum electrolytes were within normal ranges and serum creatinine was 97mmol/L.

 

A renal ultrasound scan 7 days after the onset of loin pain showed a 5cm mass in the upper pole of the right kidney.  A CT scan with contrast revealed a 5cm x 4cm low attenuation lesion in the right renal cortex (see figure 1). There was no renal vein involvement and no evidence of lymphadenopathy or pulmonary lesions.  He was informed that the mass was likely to be a malignant renal tumour. A laparascopic complete nephrectomy was performed without complication 4 weeks after initial presentation.

 

 Figure 1 Contrast enhanced, helical CT of abdomen. There is an area of low attenuation in the upper pole of the right kidney (circled).

Surprisingly, histological examination revealed an area of established renal infarction rather than neoplasm.  There was marked intimal thickening of the renal artery with evidence of dissection of the arterial wall and thrombus in the lumen (figure 2). There was no evidence of atheromatous disease.  The histological features were consistent with intimal-type fibromuscular dysplasia.

 

Figure 2 Main renal artery with marked fibromuscular thickening of the intima (I) and dissection of the vessel wall with organising thrombus (T) in the new lumen (Elastica MSB stain, x 40 magnification).

 

MRI imaging of the remaining kidney and renal artery was normal, as was a full thrombophilia screen.  The patient remains well, and normotensive with a serum creatinine of 103 mmol/l.

 

Discussion 

This case illustrates an unusual presentation of renal infarction. The delay between symptoms and investigation may have contributed to the initial misdiagnosis.

 

Loin pain is a common symptom, though renal infarction is thought to be rare.  In a prospective study of 2000 patients with typical “renal colic”, a third had no evidence of renal calculi and there were 5 cases of renal infarction.1 Loin pain investigation protocols usually involve spiral CT scanning without contrast. In order to diagnose infarction, it is essential to perform a contrast-enhanced CT scan.  Acute renal infarction has a classical appearance on contrast CT, which can change over time. In addition an elevated serum LDH level is a highly sensitive, though non-specific, finding in renal infarction and could be used as a simple initial screening test.2

 

CT is the main imaging technique for identification and diagnosis of renal mass lesions.  Pathological outcomes of 207 patients with renal masses suspicious of malignancy found on CT and removed by laparascopic nephrectomy showed that 144 (69.6%) were malignant.3 This is sufficiently high that most units will perform nephrectomy to remove suspicious lesions rather than risk malignant “seeding” with guided biopsy. None of the lesions in this series were renal infarcts.3

 

Fibromuscular dysplasia (FMD) is an uncommon cause of stenosis of small to medium sized arteries. It is classified according to the arterial layer affected:  medial-type FMD accounts for 90% of cases, intimal type <10% and periadventitial <1%.4 The renal artery is the most common site of involvement and tends to affect women aged between 15 to 50.  The incidence of FMD is unknown but recent studies investigating healthy, normotensive people as potential living kidney donors found a prevalence of up to 6.5% suggesting that most patients do not have clinical consequences.5

 

The most common complication of renal FMD is hypertension. There are fewer than 20 cases of renal infarction complicating FMD in the literature 6,7. The mechanism of infarction is not clear.  We postulate that turbulence within the irregular main renal artery led to thrombus formation and embolism to a branch renal artery. In one previous case of FMD renal infarction was associated with Factor V Leiden mutation.7  Interestingly, although FMD is more common in females, renal infarction has only been reported in males.   

 

The natural history of FMD is unknown. Hypertension should be treated with antihypertensive medication and angioplasty cures or improves blood pressure in up to 97% of cases.4  Invasive digital subtraction angiography is the gold standard investigation for diagnosing FMD.  By comparison, MRA and CT-angiography have been shown to be inferior with sensitivities of <65%.9  Given our poor understanding of the natural history of this condition, the benefit of screening in the absence of hypertension is unknown. It would be difficult to justify the risks of invasive angiography on the basis of current evidence.

 

Conclusions

Acute renal infarction should be considered in all patients presenting with acute loin pain. The radiological appearances of a renal infarct can be indistinguishable from renal tumours. Renal infarction is a rare complication of FMD.

 

Summary

References

  1. Rucker, CM, Medias,CO, Bhalla. Radiographics 2004;24:S11-28

  2. Korzets Z, Plotkin E, Bernheim J, Zissin R.  The clinical spectrum of acute renal infarction. Isr Med Assoc J   2002;4: 781-784.

  3. Link RE, Bhayani SB, Allaf ME et al. Exploring the learning, pathological outcomes and perioperative morbidity of laparascopic partial nephrectomy performed for renal mass. J Urol  2005; 173:1690-1694. 

  4. Slovut DP, Olin JW.  Current Concepts: Fibromuscular Dysplasia (Review) NEJM 2004;350:1862-71

  5. Andreoni et al. Transplantation 2002;73:1112-1116

  6. Barbey F, Matthieu C, Nseir G, Burnier M, Teta D. A young man with renal colic. J Intern Med 2003;254: 605-8 

  7.   Kirchgatterer A, Lugmayr H, Aspock G, Wallner M, Knoflach P.   Renal infarction due to a combination of fibromuscular dysplasia and factor V Leiden mutation. Nephrol Dial Transplant 2004;19;512-513.

  8. Safia RD, Textor SC. Renal Artery Stenosis. NEJM 2001; 344:431-42.

  9. Vasbinder GB et al.  Accuracy of computed tomographic angiography and magnetic resonance angiography in diagnosing renal artery stenosis.  Ann Intern Med 2004;141(9):674-82

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