Case and images Sarah Vaughan Discussion Genevieve Carbonatto
A 55 year old man presents to the ED with 5 days of loin to groin pain and microscopic haematuria.
He was started on nitrofurantoin as an outpatient for a possible UTI. A point of care renal ultrasound is performed
This is a clip through his right kidney without and then with colour Doppler.
What can you seen on these clips?
There is mild hydronephrosis
The normal renal sinus shows several echo free spaces so it is difficult to differentiate blood vessels from calyceal dilatation. In a normal kidney with no hydronephrosis there should be no echo free space in the renal sinus with colour Doppler. There are only 2 physiological situations where hydronephrosis may be present, a full bladder and pregnancy. In pregnancy this may occur as early as 12 weeks gestation and is detected in 3/4 of patient after 20 weeks.
What is the grading system for hydronephrosis and how would you grade the degree of hydronephrosis in this patient?
Hydronephrosis can be divided into 4 grades.
- Grade I : Dilated renal pelvis with no calyceal dilatation and normal parenchymal thickness
- Grade II : Dilatation of the renal pelvis and renal calyces
- Grade III: Cystic dilatation of the renal pelvis and calyces which become convex and thinning of the parenchyma
- GradeIV: The prarenchyma is no longer demonstrated
This patient has mild hydronephrosis.
Is hydronephrosis always associated with renal colic?
No, hydronephrosis is not always associated with renal colic. Unilateral hydronephrosis visible on ultrasound is present between 71% and 92% depending on different studies. In the majority of cases the hydronephrosis will be mild. The size of the stone largely determines the degree of hydronephrosis. There may be no hydronephrosis with small stones. Ultrasound looking for hydronephrosis therefore has moderate sensitivity and specificity in identifying renal stones.
A renal study also includes a bladder scan. This is his bladder scan. What can you see?
There is a stone visible at the right PUJ. The stone is identified by the acoustic shadow it produces. Small stones may not produce acoustic shadows. Stones are only visible on ultrasound in around 25% of cases
Where does point of care ultrasound fit in in the diagnosis of renal colic? We have seen that it is moderately specific and moderately sensitive in picking up hydronephrosis for renal colic and that hydronephrosis is not always present in renal colic.
It’s role lies in expediting management. If hydronephrosis is present and the clinical picture fits with renal colic then pain relief +/- CT KUB can be ordered. A CT KUB can be avoided if this is not the patient’s first presentation with renal colic. If a stone is identified then the diagnosis is confirmed.
It is also a tool in clarifying or directing the clinician to potential differential diagnoses such as pneumonia, ruptured AAA, aortic dissection, biliary colic, appendicitis, diverticulitis, ruptured ovarian cyst, ectopic pregnancy.
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