68 yo man presents with a 3 day history of pain in the right iliac fossa. This pain is classic for renal colic – comes on suddenly, gets really bad quick, pulses away for half an hour or so then goes away – leaving a dull ache in its place. Some “dark urine” noted by the patient. No fevers, no dysuria, no GI symptoms.
PMHx: type 2 DM – diet only, overweight, meat-eater, no gout, no family history of urolithiasis, no surgical history
Physical exam – not much to find: non-tender abdomen, no loin tenderness, Obs all normal (pain has disappeared)
Urinalysis: here we get to the first clinical question –
Acually – not as good as I always thought – surely if the UA is clean – there cannot be a stone right? Well wrong. Two recent studies by Xafis (Emerg Med Journ, 2008) and Kim (J. Korean Soc of EM, 2011) both came up with similar numbers.
The sensitivity, specificity , + predictive and – predictive values for microscopic haematuria (vs. CT) were: 67%, 58%, 86% and 31% in the Swiss study. Then 89.4%, 41.1, 88.9%, and 42.1% in the Korean study.
So I don’t think you can conclusively say Yeah or Nay based on a urinalysis
So we often need to do some tests to work out the answer: IS THERE A STONE?
This is an area of radiology that has evolved over the past 5 years. The old-school IVP and plain film KUBs have pretty much gone by the wayside.
In WA Health we have access to the “Imaging Pathways” resource which I find quite useful in deciding what to do next. For suspected renal colic the pathway looks like this (Click) – basically a low-dose, non-contrast CT KUB is your first step in pretty much everybody unless pregnant or you think they might have a AAA!
The combination of a plain film KUB with an US is not to be sneezed at I think. This Spanish study (European Radiol, 2004
) showed that whilst CT was more accurate than US + KUB, US was good at picking the stones that were likley to require intervention (usually the big, high ones). So if a stone passes in the night and doesn’t show on US – does it matter? Maybe not – but that is a discussion you need to have with your patient, are they (and you) comfortable with this degree of diagnostic uncertainty?
So what next – you diagnose a stone. It is 4 mm, in the lower ureter – so it should pass, in theory. What can you offer this patient to make them experience les pain and pass it quicker? This paper by Daniel Spernat and John Kourambas (BJUI, Nov 2011) has just been released online. It goes through all the therapies and evidence nicely – so read it yourself – it is not too long.
- Drink lots of water – urine output to be >2 L/day
- Citrate – works by inhibiting crystal formation / binding calcium. Take potassium citrate – it helps in other ways too…
- Avoid lots of animal protein and salt – well that is just good all round health advice!
- Calcium – you need to eat it for your bones etc, but avoid excess.
- Thiazide diuretics – decrease stones, but you should take citrate with it to avoid hypocitraturia…
- Allopurinol: decreases gout stones, but also oxalate stones – they form around gout.
- Sodium bicarb – alkalinser of urine, but it has a lot of sodium (bad) – so use K-citrate instead.
- Alpha blockers – “medical expulsion therapy” is used for distal ureteric stones. Tamsulosin seems to be the most efficacious. Though only slightly better than placebo – Study thanks Andy
- Ca-channel blocker (nifedipine) work, but not as good as alpha-blockers
- NSAIDs are good for pain relief and decrease ureteric pressure – but no difference in passage rates – oh, and watch that renal function if using these!
This cool table summarises it all in a nutshell:
Table 2. First-line agents in routine use
|Uric acid stone prevention
|Calcium stone prevention with hypercalciuria
|Cystine stone prevention
||D penicillamine or alpha mercaptopropionylglycine
|Uric acid stone dissolution
|Medical expulsion therapy
||Surgical treatment is first-line therapy
- the diagnosis of renal stone disease is a bit like the diagnosis of anaemia – there are a lot of causes out there (in there), and the diagnosis should probably trigger a search of the common aetiologies – I send off a few bloods (FBP, UEcr, uric acid, Calcium..)and try and catch a stone for analysis if I can.
- Beware the patient with a fever, septic looking or who has lots of white cells and nitrites in the UA with the blood – they are at risk of an infection and possible urosepsis – so treat them early!