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The prostatic middle lobe: clinical significance, presentation and management

Nature Reviews Urology volume 20, pages 645–653 (2023)Cite this article

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Abstract

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.

Key points

  • Various subcategories of benign prostatic hyperplasia exist, specifically, 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 clinical parameter that positively correlates strongly with the urodynamic evidence of BOO.

  • Measurement of IPP using transabdominal or transrectal ultrasonography is a discriminative evaluation that can help inform the decision to use invasive urodynamic studies.

  • Low-grade IPP can be managed conservatively with α-adrenoceptor antagonists and/or 5α-reductase inhibitors; 5α-reductase inhibitors might reduce total prostate volume but are unlikely to alter the degree of IPP.

  • High-grade IPP is the strongest predictor of failed medical therapy and conversion to surgical intervention. Patients with high-grade IPP should be offered surgery from the outset to reduce the risk of clinical progression.

  • The extent, shape and morphology of IPP might help inform the optimal surgical approach; however, more studies are needed to examine their effects on the success of bladder outlet procedures.

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Fig. 1: The enlarged middle lobe of the prostate acts as a ball valve obstructing the bladder.
Fig. 2: Classic uroflowmetry pattern in a patient with middle lobe enlargement.
Fig. 3: Radiological evidence of middle lobe enlargement.

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    Sammy Gharbieh, Fairleigh Reeves & Ben Challacombe

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S.G. researched data for the article. S.G. and B.C. contributed substantially to discussion of the content. S.G. and F.R. wrote the article. All authors reviewed and/or edited the manuscript before submission.

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Gharbieh, S., Reeves, F. & Challacombe, B. The prostatic middle lobe: clinical significance, presentation and management. Nat Rev Urol 20, 645–653 (2023). https://doi.org/10.1038/s41585-023-00774-7

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