In the short-term, rain causes instability because, like a heavy snowfall, it imposes an additional load on the snowpack; and, once rainwater seeps down through the snow, it acts as a lubricant, reducing the natural friction between snow layers that holds the snowpack together. Most avalanches happen during or soon after a storm. Daytime exposure to sunlight will rapidly destabilize the upper layers of the snowpack if the sunlight is strong enough to melt the snow, thereby reducing its hardness. During clear nights, the snowpack can re-freeze when ambient air temperatures fall below freezing, through the process of long-wave radiative cooling, or both. Radiative heat loss occurs when the night air is significantly cooler than the snowpack, and the heat stored in the snow is re-radiated into the atmosphere. Dynamics
When a slab avalanche forms, the slab disintegrates into increasingly smaller fragments as the snow travels downhill. If the fragments become small enough the outer layer of the avalanche, called a saltation layer, takes on the characteristics of a fluid. When sufficiently fine particles are present they can become airborne and, given a sufficient quantity of airborne snow, this portion of the avalanche can become separated from the bulk of the avalanche and travel a greater distance as a powder snow avalanche.
However, if no underlying cause is discovered, the hematuria should be re-evaluated with urinalysis and urine microscopy within 12 months. Additionally, for all risk categories, if a nephrologic origin is suspected, consultation of a nephrologist should be made. Pathophysiology
The pathophysiology of hematuria can often be explained by damage to the structures of the urinary system, including the kidney, ureter, urinary bladder, and urethra, and in men, the prostate. Common mechanisms include structural disruption to the glomerular basement membrane and mechanical or chemical erosion of the mucosal surfaces of the genitourinary tract. Management
Medical Emergency: Acute clot retention
Acute clot retention is one of three emergencies that can occur with hematuria. The other two are anemia and shock. Blood clots can prevent urine outflow through either ureter or the bladder. This is known as acute urinary retention. Blood clots that remain in the bladder are digested by urinary urokinase producing fibrin fragments. These fibrin fragments are natural anticoagulants and promote ongoing bleeding from the urinary tract. Removing all blood clots prevents the formation of this natural anticoagulant. This in turns facilitates the cessation of bleeding from the urinary tract.The acute management of obstructing clots is the placement of a large (22-24 French) urethral Foley catheter. Clots are evacuated with a Toomey syringe and saline irrigation. If this does not control the bleeding, management should escalate to continuous bladder irrigation (CBI) via a three-port urethral catheter. If both a large urethral Foley catheter and CBI fail, an urgent cystoscopy in the operating room will be necessary.