P7
Renal Arcuate Vein Microthombi – A New Clinico-Pathological Entity Causing Acute
Kidney Injury in Young Adults
Huda Mamoud1, Andrew Redfern1 , Tom McCulloch2, Adam Shardlow1, Matthew Hall3,
Catherine Byrne3, Nicholas M Selby1,4
1
Department of Renal Medicine, Royal Derby Hospital, 2Departments of Histopathology and
Renal Medicine, Nottingham University Hospitals, 4Division of Medical Sciences and
Graduate Entry Medicine, University of Nottingham
3
INTRODUCTION: Over the last three years, a series of patients have presented to
neighbouring East Midlands renal units with a previously unrecognised clinico-pathological
syndrome causing Acute Kidney Injury (AKI). The renal biopsy findings were distinctive and
are not widely recognised as a cause of AKI. As we identified more cases, it became clear that
there were unifying features in the clinical presentation that may differentiate this scenario from
other more common aetiologies of AKI. We aim to describe the clinical history and renal biopsy
findings of these cases, as well as describing the investigations that we have undertaken in an
attempt to identify an underlying cause.
METHODS: Description of case series.
RESULTS: Clinical presentation: The index case in 2010 and a further four of the seven cases
presented to one nephrology unit. The second two cases presented to a neighbouring nephrology
unit. All cases were young adults (median age 24yrs, range 18-35yrs). Patients had AKI stage 2
or 3 without an obvious cause. Strikingly, all described marked loin or lower back pain; imaging
in all cases was normal. Urinalysis was positive for blood in all cases and for protein in six
(urine protein:creatinine ratio 19-123mg/mmol). All five cases that presented to same unit had
consumed alcohol in moderate to large quantities within a few days of onset of symptoms (but
all denied drug use). One of the cases presenting to the second unit occurred in the setting of a
mixed overdose that included alcohol. Six patients underwent renal biopsy in view of the
clinical picture or failure to initially respond to supportive therapy.
Histopathology: In each case the findings on biopsy were similar: well defined microthrombi in
the renal arcuate veins associated with the presence of a stereotypical and unusual inflammatory
reaction at the corticomedullary junction, in the absence of any other lesions to explain AKI.
Subsequent investigations: Six patients had mildly elevated CRP (median 47mg/dl, range 1268). Immunology and microbiology screens were universally unremarkable, as were renal vein
doppler and thrombophilia screen in the index case. In the most recent case, liquid
chromatography mass spectrometry of urine did not detect any alcohols or recreational drugs
including any of the 60+ known ‘designer drugs’. A ToxBase query did not reveal any other
similar reports and a systematic review of the literature found only one previous description of
similar histopathological changes, which occurred in the setting of ecstasy ingestion.
Outcome: All patients have had complete recovery of renal function, median number of days
to a normal baseline creatinine was 17 days (range between 6-60 days) and none have had
further episodes.
CONCLUSIONS: We describe a new clinico-pathological entity causing AKI in young adults,
the cause for which is currently unclear. Awareness of this condition may help diagnosis in
other cases, preventing unnecessary investigations and avoiding treatment for other conditions.
Screening for recreational drug use should be considered in similar cases as well as storage of
admission serum and urine samples. Planned next steps are a national survey of renal units to
identify other potential cases, as well as a review of historical renal biopsy samples from
patients of similar age who also sustained AKI.