Misplaced Foley catheter in a female patient
Below is a sonographic image of transverse view of the lower pelvis showing Foley balloon (arrow) outside (posterior to) the bladder wall in a woman. What is posterior to bladder in females? – Uterus and vaginal canal! So, the Foley was misplaced in the vagina. While a conscious patient might be able to alert us that something is not right, those who are sedated cannot. Therefore, it would be prudent to exclude this situation using POCUS before starting dialysis for anuria.
Here is another scenario that can be encountered in women (more than men). Foley balloon inflated in a urethral diverticulum. Note the balloon (arrow) is anterior to the bladder in this case (depends on the location of the diverticulum). A differential diagnosis here would be that the Foley is correctly placed decompressing the bladder, but the anechoic structure is an ovarian cyst. However, if you carefully observe the sonographic image, there is nothing suggestive of decompressed bladder around the balloon (like a hypoechoic muscle or little bit of anechoic urine).