Diagnosis
Diagnosis of oligohydramnios is made by conducting a transabdominal ultrasound of the abdomen. There are two methods that can be used to make the diagnosis. The first is by using an amniotic fluid index (AFI). In this method, the sonographer measures the amniotic fluid in each of the four quadrants of the abdomen (right upper quadrant, left upper quadrant, right lower quadrant, left lower quadrant) and adds the values together. For reference, a normal AFI is 5–25 cm. An AFI <5 cm is considered oligohydramnios and an AFI >25 cm is considered polyhydramnios. Randomized control trials have shown that use of AFI can cause an increased number of false positive diagnosis of oligohydramnios and recommend using the measurement of a single deepest pocket (SDP) of amniotic fluid to diagnose oligohydramnios instead.To calculate a single deepest pocket, the sonographer scans each of the four quadrants of the abdomen looking for the deepest pocket of amniotic fluid that does not include any fetal body parts or an umbilical cord. It is measured from the 12 oclock position to the 6 oclock position. For reference, a normal SDP is 2–8 cm. A SDP <2 cm is considered oligohydramnios and a SDP >8 cm is considered polyhydramnios. The use of a SDP for diagnosis of oligohydramnios is associated with less false positives and thus less unnecessary interventions without an increase in adverse perinatal outcomes.In a multiple gestation pregnancy, measuring a single deepest pocket is the most accurate determination of adequate amniotic fluid levels.
It is chronic, lasting many years or even decades with worsening of symptoms rather than spontaneous remission. Transformation to another psychiatric condition is unlikely, although very rarely what appears to be ORS may later manifest into schizophrenia, psychosis, mania, or major depressive disorder. The most significant risk is suicide. When treated, the prognosis is better. In one review, the proportion of treated ORS cases which reported various outcomes were assessed. On average, the patients were followed for 21 months (range: two weeks to ten years). With treatment, 30% recovered (i.e. no longer experienced ORS odor beliefs and thoughts of reference), 37% improved and in 33% there was a deterioration in the condition (including suicide) or no change from the pre-treatment status. Epidemiology
Cases have been reported from many different countries around the world. It is difficult to estimate the prevalence of ORS in the general population because data are limited and unreliable, and due to the delusional nature of the condition and the characteristic secrecy and shame.For unknown reasons, males appear to be affected twice as commonly as females. High proportions of ORS patients are unemployed, single, and not socially active. The average age reported is around 20–21 years, with almost 60% of cases occurring in subjects under 20 in one report, although another review reported an older average age for both males (29) and females (40). History
The term olfactory reference syndrome was first proposed in 1971 by William Pryse-Phillips.