Imaging of urinary tract calculi

38 Imaging of urinary tract calculi



image

Fig. 38.1 This radiograph demonstrates an opacity to the left of the L3/4 disc space which represents a stone.



Background


Ninety per cent of urinary tract calculi are radio-opaque on a plain radiograph. There are several strategies for imaging suspected urinary tract calculi, which are described below.


Renal colic is a very common presentation to the on-call doctor. Infection proximal to obstruction is an emergency. Remember also that abdominal aortic aneurysms can present similarly.



Clinical features



Symptoms


There is acute loin pain, radiating to the groin. The onset of pain is usually sudden. Nausea and vomiting may also be a feature. The pain is visceral, so the patient is restless, and it is often the worst pain the patient has experienced.


Patients may have a prior history of urinary calculi.


It is important to ascertain whether the patient has signs and symptoms of infection such as pyrexia/rigors (as an obstructed infected kidney is an emergency) and whether they have a single kidney. Obstruction by a stone threatening the integrity of a single kidney is also an emergency which should be addressed immediately.


The patient may have frank or microscopic haematuria.



Signs


Loin tenderness is generally not a feature and suggests pyelonephritis.



Differential diagnosis


This is very wide and includes many causes of abdominal pain:


• pyelonephritis – usually insidious in onset; the patient is febrile, has loin tenderness on examination, and has leucocytes/nitrites/blood in urine

• appendicitis

• diverticulitis

• abdominal aortic aneurysm (Chapter 42) – ruptured or unruptured.


Radiological features


There are three methods for imaging suspected urinary tract calculi: plain radiographs, IVUs and unenhanced CT.



Plain radiographs


The traditional first line was to obtain a plain radiograph, centred on the urinary tract – a ‘KUB’ film (kidneys, ureters, bladder).


It is still useful to be able to assess such a film for ureteric calculi, as you may also detect a ureteric calculus in a patient presenting on the surgical ‘take’ with abdominal pain. But this is now not the first-line investigation if stones are suspected.


A knowledge of the course of the ureter is important for proper assessment of a plain film of the abdomen (see Chapter 28).


Any calcific density along the course of the ureter should be considered as a potential ureteric stone.


Phleboliths – small calcifications in the pelvic small vessels – can be confused with stones but they are generally completely round, and have lucent centres.

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Aug 20, 2016 | Posted by in ULTRASONOGRAPHY | Comments Off on Imaging of urinary tract calculi

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