Beware of making the diagnosis of renal colic!

Sometimes a little knowledge can be dangerous. Beware of just knowing the percentages, know to apply them in the clinical context.

I was recently handed over a patient who had presented with abdominal pain. The patient was reported as having some left sided abdominal pain and pain on left kidney ballottement. The diagnosis of renal colic colic had been made. The patient was being treated with oral analgesia with a view to going home when pain was under control.

The past history the patient gave was a hysterectomy a few years prior, with a complication of hernia, and a further complication of infection, post hernia repair. She also had a secondary in the lung for which she had had a lobectomy. She did give a history of left renal colic some 19 years previously.

On handover, the question I asked was if there any blood in the urine. “No.” Hmmm. I always start to think. Now I know and was told, yet again, that a percentage of patients don’t have blood in the urine. But, when I hear no blood, I get suspicious and start looking. More about that in a minute.

Renal colic is such a common condition that I thought it would be good to do a quick 2 minute review.

How does Renal Colic Present?

PAIN – Character and Intensity

Pain in renal colic is usually caused by renal capsule distension secondary to obstruction. The pain can wax and wane as the ureter spasms and the pain can vary in intensity, from severe to very mild.

PAIN – Position

The position of the pain changes depending on where the stone is; upper obstruction results in pain in the flank, whereas lower obstruction may produce pain in the testiclws or labium.

HAEMATURIA

Haematuria, I consider to be the most important distinguishing feature. It is present in a significant number of patients but can be absent in up to 30% of cases. This is also associated with time to presentation, such that the percentage drops with time from a potential 95% plus at day one to 70% at day 3.

HOW ABOUT DYSURIA AND URGENCY?

Yes, these can occur especially if the stone is in the distal ureter. Beware that there is no intercurrent infection with a stone as this is significant.

Beware the mimics.

There are some things that can fool us and we need to be wary of these. There are the rarer conditions such as renal cell carcinoma bleeding and causing obstruction. There are other conditions such as ectopics or appendicitis, however putting these together with vitals and a good history should give the diagnosis.

Potentially the trickiest one is aortic aneurism, given that up to 40% of cases of a leaking abdominal aortic aneurysm will have blood in the urine. Also significant is that in a number of cases, you cannot palpate a pulsatile aorta. So beware.

INVESTIGATIONS

Non-contrast CT is the gold standard, being able to visualise stones not seen by KUB or IVP as well as potentially offering alternative diagnoses. The pail KUB is fine if we are looking at a radio-opaque stone and monitoring its progress, but not very good for the lucent uric acid stones. The IVP, although good for showing obstruction is not as sensitive as CT and exposes the patient to a higher dose of radiation.

Ultrasound is the investigation we might choose in a pregnant patient as it will demonstrate obstruction and does not expose the patient to radiation.

Back to the case.

On examination, the patient was actually more tender midline and although there was pain on ballottment, the pain seemed to involve the lateral abdomen above the kidney rather than the kidney itself. Bloods were essentially normal.

I asked for a surgical consult, as I was concerned that this was something else and not renal colic and waited surgical review.

Following review, the surgeons stated that this was a left renal colic, given the ballottement pain and previous history of renal colic on the same side. Also again, the patient doesn’t have to have blood in the urine. Although I was being told I was wrong, this particular surgical registrar was a kind gentleman and didn’t make me feel like a moron, like so many other surgical registrars try to.

Still doubt in my mind. OK, CT KUB here I come. Radiology registrar says, “Why do you want a CT KUB? Stone diagnosed by surgical registrar and patient’s pain is minimal and we are swamped.”

“OK – I understand but she does have this metastases history and no blood in the urine…and we have to do it.”

Registrar does the CT.

NO stone. Inflamed fatty tissue with sentinel loop in the abdo, indicating entrapment in a hernia. The patient went to the operating room.

This case is about thinking when not all signs match up.

So previous abdo history, examination was not classical renal colic and there was some midline abdominal pain and no blood in the urine.

Beware making the diagnosis of renal colic if you’re not sure. Now in this case, the patient would have probably declared herself regardless, because we would not have been able to control her pain and she would have needed an admission and would have gotten a CT at some stage. But it’s important to get in early. The worst thing that could have happened was that she may have been sent home with significant oral analgesia and returned, septic and very unwell.

Remember, the knowledge you take into your shift does matter!