Appendicitis or Renal Colic

UA was negative except for 1+ red cells 

WCC normal, CRP normal

Bedside US was negative for pelvic free fluid of masses. However, renal US revealed:

R kidney (long)

This image shows grade 2 hydronephrosis: dilated renal pelvis and ureter and distended calyces. But notice the renal cortex is normal thickness. Also the calyces do not look clubbed, they maintain their normal branching structure. The left kidney was normal. 

Grades of hydronephrosis: Grade 1: dilated pelvis and ureter only; Grade 2: + dilated calyces, but not clubbed; Grade 3: + clubbed cayces but normal cortical thickness >1cm; Grade 4: + thin cortex

The degree of hydronephrosis isn't always a reliable indicator of the degree of obstruction because it is also determined by the duration of obstruction and the degree of hydration. But typically, significant obstruction leads to higher grade hydronephrosis.  

Examination of the bladder revealed a small hyperechoic linear structure at the VUJ (likely renal stone). Colour doppler on this revealed twinkle artefact which is typical for renal stones.

Pelvis (trans) showing R VUJ stone with twinkle artefact - annotated below

Intraureteric stones are typically seen best at the PUJ or the VUJ with ultrasound. The midureter is usually obscured by bowel gas. Ureteric stones are usually hyperechoic and colour doppler reveals a tail of vibrant colour reveberation artefact called the "twinkle" artefact. Often at the VUJ, the stones are small and blend in with the bladder muscle so decreasing gain to make the soft tissue hypoechoic and adding colour can increase your sensitivity. A full bladder also helps.

Pelvis trans: hyperechoic stone in R VUJ

Note that the measured size of a stone on US is usually unreliable. 

Given the patient remained painfree and the stone was very distal, she was discharged home without further imaging. 

For more information on scanning the kidneys for hydronephrosis, click on the button below.