Some other helpful clues you may see in urine:

Stones

80% of renal calculi (stones) are composed of calcium compounds eg Calcium Oxalate. These cause pain as they are hard, sometimes sharp, and are being squeezed through a piping system designed to accommodate fluids only. They can cause trauma and bleeding as they are passed, or if they become stuck can result in serious infection, and damage to the kidney above the blockage. If you see one that has passed, there may be more.

Bubbles / faeces

High protein content may make the urine bubbly. This can be seen in renal disease where there is excess leakage through damage to this filtering organ.

The bladder is a closed system with no air, and so there should not be gas in the urine. An abnormal connection between the bowel and bladder known as a fistula, can result in faeces and air (flatus) in the urine. This may cause recurrent infections. Fistulas can develop when there is inflammation of the bladder or bowel at a point they are touching, eg caused by infection, cancer, or previous surgery.

Note: soap and other cleaning agents on a loo may make bubbles as you pee, as can simply the impact of urine into toilet water at pressure. Always interpret signs in context!

Cloudyness

Cloudy urine, that may be darker, or more strongly smelling, suggests infection. Symptoms may include urinary frequency (a need to pee more often), dysuria (burning/stinging when peeing), and pus discharging from the urethra. Infection is more common in women due to a shorter urethra for bacteria to climb from the outside world to the bladder. Also contributing is the anatomical proximity of the urethra to the anus (and thus faeces). This is why wiping from front to back is important for hygiene, so faecal bacteria are not brought into contact with the urethra.

Clots

Clots suggest bleeding, which may arise from the urinary system or gynaecological organs in women. Bleeding in the urinary tract is covered in this article.