Thanks to Dr Serena Rovida for this great case and images.
A female in her 30’s presented with a 2 day history of right flank pain and vomiting, 2 days following her LMP. No urinary/bowels symptoms. Examination was unremarkable aside from some right flank tenderness.
A POCUS scan of her abdomen showed the following images:
What do they show and what is the diagnosis?
-The Left kidney appears normal.
-The Right kidney shows a markedly dilated renal pelvis and ballooning of the calyces consistent with moderate-severe hydronephrosis. There is a small rim of peri-nephric oedema (hypoechoic area – more visible on the video clip)
-The bladder is not overly distended. There is a hyperechoic structure at the right Vesico-ureteric junction consistent with a ureteric stone. This is confirmed on the doppler image where it displays the ‘twinkling artifact’ & ‘colour comet tail’ which are very sensitive for identifying small stones (see below).
Outcome: The patient’s renal function was normal and after discussion with urology she was admitted to CDU for analgesia.
Urinary Tract POCUS: (Level 2 modality)
Emergency Physicians with appropriate training have been shown to have a moderate-high sensitivity for identifying hydronephrosis with POCUS (although less so for mild hydronephrosis), and the presence of mod/severe hydronephrosis is highly specific for the presence of stones and suggestive of larger stones (>5mm), although bear in mind there are other conditions that may also cause hydronephrosis.
For those with some Level 1 experience, we already have some appreciation of how to find and identify the kidney and bladder as part of the FAST scan. The kidneys are best visualised with more posterior probe placement, and views can be improved by asking the patient to take a deep breath and hold, or by turning into the lateral decubitus position.
- Assess longitudinal size of kidneys
- Assess parenchyma for abnormalities. Ensure to pan through the whole kidney in both longitudinal and transverse planes to fully assess the renal parenchyma
- Assess for hydronephrosis
- Assess for bladder size
- Assess for the presence/absence of ureteric jets – presence of bilateral ureteric jets suggests against ureteric obstruction.
‘Twinkling Artifact’ & ’Colour Comet Tail Artifact’:
-Colour Doppler ultrasound facilitates the detection of urinary stones. Specifically, the presence of a ‘twinkling artifact’ is suggestive of the presence of urinary stones. The twinkling artifact is a colour Doppler phenomenon that appears as a rapid change of colour immediately behind a stationary object and may have an associated ‘colour comet-tail artifact’. This sign is diagnostically useful, especially in urolithiasis and can aid the grey scale ultrasound detection of a urinary calculus, especially if the stone is indistinguishable from the surrounding structures or lacks a posterior acoustic shadow.
- Pathan SA et al. Emergency Physician Interpretation of Point-of-care Ultrasound for Identifying and Grading of Hydronephrosis in Renal Colic Compared With Consensus Interpretation by Emergency Radiologists. Acad Emerg Med. 2018 Oct;25(10):1129-1137. doi: 10.1111/acem.13432. Epub 2018 May 28. PMID: 29663580.
- Wong C, Teitge B, Ross M, Young P, Robertson HL, Lang E. The Accuracy and Prognostic Value of Point-of-care Ultrasound for Nephrolithiasis in the Emergency Department: A Systematic Review and Meta-analysis. Acad Emerg Med. 2018 Jun;25(6):684-698. doi: 10.1111/acem.13388. Epub 2018 Mar 25. PMID: 29427476.