The left lower part of the navel is the left ureter, part of the rectum, bladder, and other organs. As there are multiple organs, a regular health examination at a hospital as per medical advice is required to clarify the health condition.

1. Left ureter: There are left and right ureters, which can maintain the physiological function of the human body.

2. Part of the rectum: It is the upper part of the rectum, and after eating, food residue will be excreted from the body through the intestinal peristalsis.

3. Bladder: It can store urine, and when the bladder is full, there will be a sense of urination.

In addition, some parts of the small intestine, sigmoid colon, and left ovary, among other organs, require a urinary system ultrasound examination at a hospital to clarify the health condition.