McArdle
KA1, Ray D2.
1.
Department Of Surgery, New
Cross Hospital, Wolverhampton, West
Midlands,WV4 5HN.
2.
Dept of Urology, Russells Hall Hospital,
Dudley, West Midlands, Dy1
2HQ.
Correspondence
to: Miss
Kirsten A McArdle, Department
Of Surgery,
New Cross Hospital, Wolverhampton,West
Midlands,WV4 5HN.
e-mail
kirstenmcardle@hotmail.co.uk
SMJ 2008 53(2): 66
Abstract:
Although
haematuria is the commonest cause of red urine, it is important to recognise
that it is not the only cause. We
report the case of a 62 year old lady with a prosthetic heart valve who
presented to the haematuria service with red urine resulting from haemolysis
secondary to a peri-valvular leak.
Case
Report:
A
62 year old lady presented to the rapid access haematuria clinic with a seven
day history of passing red urine. She
had no other urinary symptoms or pain and denied passing blood clots in her
urine. She did however complain of general fatigue, loss of appetite and some
weight loss over the preceding weeks. There was no previous history of
haematuria or urological disease. Her past medical history included a mitral
valve replacement, for which she was taking warfarin.
A
urine sample taken at the clinic was bright red in colour.
Urine dipstick was strongly positive for the presence of blood.
Initial laboratory investigations found her to be anaemic with a
haemoglobin of 7.7g/dl. Her renal function was found to be normal and her INR
was within the normal therapeutic range for valve protection.
A
flexible cystoscopy revealed normal bladder mucosa.
A CT scan of the abdomen and pelvis failed to show any abnormalities.
Laboratory urine cytometry and culture showed no evidence of infection and urine
cytology showed no evidence of malignant cells.
Despite these negative findings, the patient continued to pass red urine and drop her haemoglobin concentration. Her warfarin therapy was therefore stopped and further investigations arranged. She underwent an immunological screen, renal angiography, bilateral ureteroscopy and retrograde pyelography. However, these investigations also failed to demonstate any abnormalities.
Further
blood analyses showed a rise in serum lactate dehydrogenase and a fall in serum
haptoglobin. Her bilirubin was also found to be mildly elevated. More detailed inspection of the urine at microscopy showed
0-1 erythrocytes per high-powered field, 20-30% of which were dysmorphic.
This pattern of results suggested the presence of intra-vascular
haemolysis.
An
echocardiogram was performed. This
confirmed significant mitral regurgitation. The patient was prepared for a redo-mitral
valve replacement. At surgical exploration, a perivalvular leak was found and
repaired. Following this procedure, the urine returned to a normal colour and
the anaemia resolved. The patient made a good post operative recovery and was
discharged home. She has not had any further episodes of pigmented urine.
Discussion:
It
is essential for all patients who present with apparent haematuria to undergo
full investigation the urinary tract. Haematuria is the commonest cause of red
coloured urine. However, it is not
the only cause. For example, it is
well recognised that ingestion of beetroot1 and certain drugs such as
metronidazole, L-dopa and rifampicin2 can lead to a reddish
discolouration of the urine. Furthermore, haemoglobinuria resulting from
haemolysis or the urinary excretion of myoglobin after trauma can mimic frank
haematuria3. It is
important to recognise that urinary dipstick testing for blood is often positive
in these other conditions and does not necessarily indicate the presence of red
blood cells.
There
is a high incidence of intravascular haemolysis associated with mechanical
prosthetic cardiac valves. In the majority of cases this becomes apparent in the
first few months following insertion of the prosthesis4. Studies have suggested that up to 26% of patients with
mechanical heart valves develop subclinical haemolysis in the first 12 months
post operatively. This is suggested by rising LDH levels and falling serum
haptoglobin levels5. Significant
haemolysis is usually an indicator of a perivalvular leak. When the haemolysis
becomes severe, free haemoglobin exceeds the haptoglobin binding capacity and is
excreted in the urine. If levels are high enough, this can result in deeply
pigmented urine mimicking frank haematuria.
This
case highlights the importance of performing a formal urine microscopy rather
than relying on urine dipstick to make a diagnosis of haematuria. The absence of
abnormal numbers of erythrocytes in the urine should alert clinicians to the
possibility of a diagnosis other than haematuria. Therefore, this simple test is
essential in establishing the correct diagnosis and avoiding unnecessary and
sometimes invasive urinary tract investigations.
In
summary, it is important for clinicians to be aware that red coloured urine is
not always caused by haematuria. If
no urinary tract pathology is identified, it is important to consider
intravascular haemolysis as a potential cause of red coloured urine, especially
in patients who have prosthetic heart valves.
References:
1.
Pearcy RM, Mitchell SC, Smith RL. Beetroot and red urine.
Biochem Soc Trans. 1992 Feb;20(1):22S
2. Snider DE Jr, Farer LS.
Rifampin and red urine. JAMA.
1977 Oct 10;238(15):1628.
3. Kreder KJ Jr and Williams RD.
Urologic Laboratory Examination. Tanagho
EA, McAninch JW (Editors), Smiths
General Urology (16th Edition)
Lange
Medical Books/ McGraw-Hill 2004: 49-61.
4. Mecozzi G, Milano AD, De Carlo M, Surrentino F, Pratali S,
Nardi C, Borotolli U. Intravascular
haemolysis in patients with new generation prosthetic heart valves: a
prospective study. J.Thorac.
Cardiovasc. Surg, 2002 Mar, 123(3) 550-6
5. Lam,BK, Cosgrove DM, Bhudia SK, Gillinov AM. Haemolysis after mitral valve repair: mechanisms and treatment. Ann Thoracic Surg 2005 Feb; 79(2): 754