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Keywords:

  • fibromuscular dysplasia;
  • hypertension;
  • renal infarction;
  • urolithiasis

Abstract.

  1. Top of page
  2. Abstract.
  3. Case report
  4. Discussion
  5. Conflict of interest statement
  6. References

We report the case of a 35-year-old man with no cardiovascular morbidity, presenting with acute flank pain, microscopic haematuria and normal blood pressure. Initially diagnosed as a ureteral colic, the patient was recovered 6 weeks later with severe hypertensive crisis. Further investigations revealed a massive renal infarction secondary to medial fibromuscular dysplasia (FMD). Several aspects of this presentation are intriguing. Renal infarcts are usually seen in older patients having cardiac problems and/or major atheromatous plaques. In addition, FMD is mainly observed in young females and rarely progresses to renal artery occlusion. Furthermore, in this case, FMD remained silent until the acute renal infarction occurred, despite a significant kidney size reduction at the time of diagnosis. Finally, the observation of a delayed hypertensive response to a major renovascular insult provides incentives to discuss possible pathophysiological mechanisms involved in renovascular hypertension.


Case report

  1. Top of page
  2. Abstract.
  3. Case report
  4. Discussion
  5. Conflict of interest statement
  6. References

A 35-year-old man, with no previous history of cardiovascular disease or abdominal trauma, was examined by his family doctor because of an acute pain in the left flank. On physical examination his blood pressure was 130/80 mmHg on both arms and the left costo-vertebral angle was tender. Urine analysis revealed microscopic haematuria. Plain abdominal radiography showed a single calcification in the left lumbar area. On abdominal ultrasound, neither renal stone nor hydronephrosis were seen but the radiologist reported a dilated proximal left ureter, suggesting a possible obstructive urolithiasis. Surprisingly, the left kidney was smaller than the right one (9.9 × 6.0 cm vs. 12.0 × 6.7 cm, respectively). In addition, intravenous pyelography (IVP) showed absence of contrast in the left kidney after 50 min. Despite these abnormalities, no late IVP images or blood analysis were made and the diagnosis of obstructive left ureteral stone was proposed. Diclofenac and norfloxacin were prescribed and the patient was discharged. Flank pain disappeared within 24 h.

Six weeks later, the patient presented intense, pulsatile headache, accompanied by nausea and vomiting and was admitted in the emergency department at our hospital. Physical examination revealed severe arterial hypertension of 210/130 mmHg without papilloedema and/or focal neurological signs. Axillary temperature was 37.4 °C. Blood analysis showed an increase in serum creatinine (127 μmol L−1), urea (9.1 mmol L−1) and total proteins (87 g L−1). Total cholesterol was 5.7 mmol L−1, HDL cholesterol 1.2 mmol L−1 (total cholesterol/HDL cholesterol ratio: 4.7), and triglycerides 0.7 mmol L−1. White cell count (9.0 G L−1), platelet count (336 G L−1), haemoglobin (160 g L−1), calcaemia (2.4 mmol L−1), serum albumin (48 g L−1), creatine kinase (CK) (57 U L−1), aspartate amino-transferase (ASAT) (13 U L−1), alanine amino-transferase (ALAT) (12 U L−1), and C-reactive protein (CRP) (4 mg L−1) were in the normal range. Sodium (134 mmol L−1), potassium (2.9 mmol L−1), and chloride (94 mmol L−1) levels were decreased. Urinary sediment and urinary catecholamines/metanephrines were within normal limits. Renal ultrasound showed a further reduction of the left kidney size when compared with previous measurements (length of 8.1 cm vs. 9.9 cm).

Renal artery duplex images showed a dramatic decrease of arterial blood flow in the main renal arteries on the left kidney. Renal angiography was subsequently performed, disclosing an aspect of stump of the left trunk, subocclusion of the superior arterial branch with multiple stenosis of secondary branches and complete thrombosis of the inferior branch (Fig. 1). The whole picture was compatible with subtotal renal infarction and secondary renovascular hypertensive crisis. To our surprise, a detailed analysis of renal arteriography revealed a string-of-beads appearance of the superior arterial branch, consistent with medial fibromuscular dysplasia (FMD). The right renal artery was normal. Thus, the hypothesis that FMD of the left renal artery ultimately lead to arterial occlusion and massive renal infarction was forwarded. In order to assess the viability of left renal parenchyma, radionuclide imaging was performed. Residual left kidney function was <5%, leaving to the right kidney most of the renal function by compensation hypertrophy. Unfortunately, the complexity of renal artery lesions (multiple intra-renal arterial stenosis and thrombosis) together with the observation of a rapidly progressing renal atrophy did not justify any angioplasty, stenting procedures or surgical reconstruction.

image

Figure 1. Angiography of the left kidney: subocclusion, with string-of-beads appearance, of the superior arterial branch; complete thrombosis of the inferior branch.

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Lisinopril 20 mg day−1 was prescribed and blood pressure dramatically decreased. Cardiac echography excluded left ventricular hypertrophy and there was no hypertensive retinopathy. At discharge, arterial pressure was 115/75 mmHg and the biochemistry values were normalized. Angiotensin-converting enzyme (ACE) inhibitors were maintained and, after 1-year follow-up, blood pressure, renal function and urinalysis were normal.

Discussion

  1. Top of page
  2. Abstract.
  3. Case report
  4. Discussion
  5. Conflict of interest statement
  6. References

The clinical presentation – acute flank pain and microscopic haematuria in a young man – suggested an ureteral colic, rather than a massive renal infarction. More than 90% of the patients presenting with a renal infarction have a medical history revealing a high risk of thromboembolism, i.e. atrial fibrillation, previous embolism, valvular or ischaemic heart disease [1], which was not the case in our patient. In addition, the initial absence of hypertension was misleading. Solez observed that hypertension was almost an universal finding in extensive unilateral or bilateral renal infarctions [2].

The presence of haematuria in the setting of acute flank pain is not very helpful indeed. Haematuria is actually a poor predictor of ureterolithiasis. In a recent report, 35% of patients with acute flank pain associated with microscopic haematuria did not have renal calculi [3]. Other diagnosis were urinary infections, ureteral tumour, torsion of ovarian masses, appendicitis and diverticulitis. Renal infarcts were not identified in that retrospective analysis of 195 patients, which confirms that this diagnosis is probably rare. In our patient, the key finding was the total absence of contrast after 50 min on IVP associated with a reduced-size kidney. Such results were not compatible with an obstructive lithiasis. Thus, the absence of a typical clinical constellation and the suboptimal interpretation of IVP and renal ultrasound lead to a wrong diagnosis of ureteral colic. As a matter of fact, the diagnosis of acute renal infarction is often delayed or missed because of unspecific clinical presentation and a relatively low incidence [1]. Most patients presenting with acute unilateral flank pain or abdominal pain are recognized to have more common diseases, such as urolithiasis, appendicitis, lumbago, or even myocardial infarction. Main laboratory abnormalities, such as leucocytosis, elevated serum LDH and CK and haematuria are common, nonspecific, and therefore not helpful [1]. Slight elevation of serum creatinine is frequently seen initially even if the renal infarct is unilateral [4].

FMD is a small- and medium-sized arterial disease that occurs more frequently in young Caucasian women, leading to nonatheromatous and noninflammatory arterial stenosis; the right renal artery is most often involved [5]. Histological subtypes include medial (70–90% of cases), intimal, and periadventitial forms [6]. In our case, FMD affected a young man, on the left side, and lead to renal infarction, which is an exceptional event [7, 8]. Although progression of FMD has been confirmed in a substantial number of patients with renovascular disease, Meaney et al. reported that in a long survey up to 10 years, progression of lesions was observed in only 16% of patients with FMD compared with 36% of patients with atherosclerosis [9]. Other studies demonstrated that progression of renovascular FMD was seen in 36–38% of patients, without however reaching complete occlusion of the vessel [10, 11]. Schreiber et al. followed 66 patients with medial FMD for 45 months and found that none of them progressed to complete arterial occlusion, although some lesions became more stenotic [12]. In the series of the Mayo Clinic, progression was more common in intimal and peri-adventitial rather than in medial FMD subtypes [13]. Furthermore, in contrast to medial FMD, intimal and periadventitial subtypes were sometimes associated with progressive dissection and thrombosis, resulting in renal arterial occlusion [9]. The relatively slow progression of the disease over time and the rarity of arterial occlusions are unexplained. The cause of FMD is not known. The disease is not seen in children and clinical manifestations generally occur during the third and fourth decade, mainly in Caucasian females. The hormonal status is believed to play a pivotal role in the development of FMD lesions. In this particular case, the picture was compatible with an occlusion of the main renal artery, as suggested by the observation of a total absence of contrast on IVP after 50 min. This event was likely to be secondary to a superimposed thrombus on a previously narrowed artery.

The two-step course of hypertension in this patient is quite instructive. The first ultrasound demonstrated that the left kidney was reduced. This observation might suggest preceding parenchymal ischaemia. However, the absence of ventricular hypertrophy and of hypertensive retinopathy together with the observation of an initially normal blood pressure suggest that the patient did not have sustained hypertension. Mechanisms responsible for sustained renovascular hypertension differ upon whether one or both kidneys are affected by vascular lesions, either pathological or created in animal models using clips. In the two-kidney one-clip Goldblatt model, the presence of a normal controlateral kidney has important consequences [14]. As the renin–angiotensin–aldosterone system is activated by the affected kidney, the controlateral kidney is exposed to elevated arterial pressures and responds by excreting sodium in far greater quantities than the stenotic kidney. So, renin activity from the nonstenotic kidney is suppressed to reduce arterial pressure.

The record of a normal blood pressure in the context of a massive renal infarction is another intriguing observation. In animal models, complete occlusion of the renal artery is usually associated with the development of hypertension within hours [14]. Irreversible renal parenchymal damage is observed after only 3 h. In this patient, the main renal artery occlusion induced a total flow stop for at least hours, probably days. So, we hypothesize that, without an effective parenchymal circulation, the infarcted kidney might not have been capable of releasing circulating vasoactive mediators. Six weeks later, when the renal artery was partially re-canalized, as demonstrated in Fig. 1, severe hypertension was observed. The intense activation of the renin–angiotensin–aldosterone system was corroborated by the presence of hypokalaemia associated with accelerated hypertension.

Prompt recognition of an acute renal artery occlusion is mandatory since treatment, i.e. thrombolysis, embolectomy or percutaneous transluminal renal angioplasty (PTRA), may minimize the loss of renal function [15]. Development of collateral vessels is crucial since maintenance of tissue viability is ensured, although perfusion is inadequate to produce urine [16]. This suggests that an attempt to revascularize occluded vessels is warranted, despite several hours or days of complete occlusion. Angiography or MR angiography are the most appropriate technique to show a delayed nephrogram through collateral circulation. In our patient, the rapid decrease of renal length (from 9.9 to 8.1 cm) during a 6-week period was compatible with significant ischaemic degenerative lesions of the renal parenchyma. In addition, angiography revealed multiple intra-renal arterial stenosis and thrombosis which rendered angioplasty or surgical reconstruction totally hazardous and probably dangerous. With regard to hypertension, if interventional therapy is not indicated or impossible, ACE inhibitors like in our case, or AT1 receptor antagonists should be the first choice antihypertensive drugs provided the disease is unilateral.

In conclusion, this educational case suggests that, in a young patient, the triad – acute flank pain, microscopic haematuria and ipsilateral normal or reduced kidney size on ultrasound – may suggest a wrong diagnosis of urolithiasis. In the absence of clear confirmation on initial investigations, angiography (or contrast-enhanced CT) should be performed to look for renal infarction and/or renal artery abnormality. The initial absence of hypertension does not preclude the existence of FMD and/or concomitant renal infarction.

Conflict of interest statement

  1. Top of page
  2. Abstract.
  3. Case report
  4. Discussion
  5. Conflict of interest statement
  6. References

No conflict of interest was declared.

References

  1. Top of page
  2. Abstract.
  3. Case report
  4. Discussion
  5. Conflict of interest statement
  6. References
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