The prostatic middle lobe: clinical significance, presentation and management.

The role of the prostatic middle lobe in the presentation and management of benign prostatic hyperplasia (BPH) is under-appreciated. Middle lobe enlargement is associated with intravesical prostatic protrusion (IPP), which causes a unique type of bladder outlet obstruction (BOO) via a 'ball-valve' mechanism. IPP is a reliable predictor of BOO and the strongest independent factor for failure of medical therapy necessitating conversion to surgical intervention. Men with middle lobe enlargement tend to exhibit mixed symptoms of both the storage and the voiding types, but symptomatology will vary depending on the degree of IPP present. Initial assessments such as uroflowmetry and post-void residual volumes are inadequate to detect IPP and could confound the clinical picture. Radiological evaluation of prostate morphology is key to assessment as it provides important prognostic information and can help with operative planning. Treatment strategies employed for BPH should consider the shape and morphology of prostate adenomata, specifically the presence of middle lobe enlargement and the degree of associated IPP.