This may occur from either a triggering event such as exposure to blood, pain, strong feelings, or a specific activity such as urination, vomiting, or coughing. Vasovagal syncope
Vasovagal (situational) syncope is one of the most common types which may occur in response to any of a variety of triggers, such as scary, embarrassing or uneasy situations, during blood drawing, or moments of sudden unusually high stress. There are many different syncope syndromes which all fall under the umbrella of vasovagal syncope related by the same central mechanism. First, the person is usually predisposed to decreased blood pressure by various environmental factors. A lower than expected blood volume, for instance, from taking a low-salt diet in the absence of any salt-retaining tendency. Or heat causing vaso-dilation and worsening the effect of the relatively insufficient blood volume. The next stage is the adrenergic response. If there is underlying fear or anxiety (e.g., social circumstances), or acute fear (e.g., acute threat, needle phobia), the vaso-motor centre demands an increased pumping action by the heart (flight or fight response). This is set in motion via the adrenergic (sympathetic) outflow from the brain, but the heart is unable to meet requirements because of the low blood volume, or decreased return. A feedback response to the medulla is triggered via the afferent vagus nerve. The high (ineffective) sympathetic activity is thereby modulated by vagal (parasympathetic) outflow leading to excessive slowing of heart rate. The abnormality lies in this excessive vagal response causing loss of blood flow to the brain.
A urethrovaginal fistula is an abnormal passageway that may occur the urethra and the vagina. It is a sub-set of vaginal fistulas. It results in urinary incontinence as urine continually leaves the vagina. It can occur as an obstetrical complication, catheter insertion injury or a surgical injury.It is also called a urethral fistula and may be referred to as UVF. They are quite rare. In the developed world, they are typically due to injuries due to medical activity. == References ==