Anatomy, Abdomen and Pelvis, Bladder Detrusor Muscle


Article Author:
Peter Sam


Article Editor:
Chad LaGrange


Editors In Chief:
Susan Jeno
Renato Vilella
Sarah Fabiano


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Kyle Blair
Trevor Nezwek
Radia Jamil
Erin Hughes
Patrick Le
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Hassam Zulfiqar
Navid Mahabadi
Hussain Sajjad
Steve Bhimji
Muhammad Hashmi
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Abbey Smiley
Sarosh Vaqar
Mark Pellegrini
James Hughes
Beata Beatty
Daniyal Ameen
Altif Muneeb
Beenish Sohail
Nazia Sadiq
Hajira Basit
Phillip Hynes
Komal Shaheen
Sandeep Sekhon


Updated:
11/13/2018 11:53:33 PM

Introduction

The walls of the bladder are mainly formed of detrusor muscle which allows the bladder to contract to excrete urine or relax to hold urine. At the inferior end of the bladder, the detrusor muscle is continuous with the internal urethral sphincter. The combination of detrusor contraction and urethral sphincter relaxation leads to urination. The detrusor muscle is under control from the autonomic system and is composed of smooth muscle. Detrusor muscle pathology can lead to urinary retention, incontinence or a combination of both. Abnormalities of the detrusor muscle if left untreated, can lead to deterioration of the upper urinary tracts.[1][2]

Structure and Function

The main function of the detrusor muscle is to contract during urination to push the urine out of the bladder and into the urethra. The detrusor will relax to allow urine to be stored in the urinary bladder.

Embryology

The bladder is initially derived from the upper segment of the urogenital sinus in the fetus and connected with the allantois. However, the allantois is eventually obliterated to become the urachus leaving just the bladder. Detrusor smooth muscle is of mesoderm and neural crest origin.

Blood Supply and Lymphatics

The upper portion of the urinary bladder is supplied primarily by the superior vesical artery (a branch of the hypogastric artery). The lower portion is supplied by the vaginal and inferior vesicular arteries in female and male respectively. There is minor supply via the inferior gluteal and obturator arteries. The venous system is drained via the vesical venous plexus, which drains into the vesical veins which eventually leads to the internal iliac veins. The lymphatics of the bladder mostly drain to the external iliac lymph nodes.

Nerves

The detrusor muscle is under autonomic control. The parasympathetic nervous system stimulates the muscarinic stretch receptors in the bladder through the pelvic nerve fibers. When urine fills the bladder, the M3 receptors located within the bladder are stretched and stimulated, which lead to contraction of the detrusor muscle for urination. At the same time, the parasympathetic fibers inhibit the internal urethral sphincter, which causes relaxation allowing for bladder emptying. During ejaculation, the sympathetic response leads to contraction of the internal urethral sphincter, to prevent reflux of semen into the bladder. This response also prevents urine from passing during ejaculation. The most sensitive region of the bladder for the stretch receptors is the trigone. When the bladder is emptied of urine, the stretch fibers are inactivated, and the sympathetic nervous system is stimulated to activate the beta-3 receptors through adenylyl cyclase-cAMP pathway in the bladder through the hypogastric nerve to cause relaxation of the detrusor muscle. Newer beta-3 agonists utilize this pathway to treat bladder overactivity. Sensory fibers detect pain from overdistention. The center for coordinating urination is located in the pons.[3][4]

Muscles

The detrusor muscle is located within the walls of the bladder and is composed of smooth muscle fibers that are longitudinal and circular. The layers of the detrusor muscle start longitudinally in the inner layer which becomes circular in the middle layer and then longitudinal again in the outer layer. The muscle is continuous with the internal urethral sphincter, which is also composed of smooth muscle. The ureter passes obliquely through the detrusor muscle to prevent back reflux of urine into the kidney as the bladder fills. If this ureteral tunnel is not oblique, or short, then urine can reflux into the kidney causing infections, renal scarring, and renal damage.

Physiologic Variants

Pediatric detrusor muscle has less contractility and has more passive stiffness compared to adult detrusor muscles. This is most likely due to a greater connective tissue to smooth muscle ratio in children. This is known as bladder compliance (change in bladder pressure/change in bladder volume). Poor (decreased) bladder compliance is associated with upper urinary tract damage.

Surgical Considerations

Pelvic surgery may lead to bladder dysfunction. Some pelvic surgeries that have reported complications of bladder dysfunction include but are not limited to radical prostatectomy, perineal resection, radical hysterectomy, and proctocolectomy. Surgeons should take caution during pelvic surgery to avoid damage to any nerves, vessels, or structures of the bladder or urinary system.[5][6]

Clinical Significance

Patients with urinary retention usually present with difficulty voiding, a sensation of incomplete emptying, urinary retention, frequent voiding, and overflow incontinence. Diabetes mellitus and other neurologic conditions such as a stroke are the main causes of detrusor nerve control degeneration. Detrusor areflexia is the inability for the bladder to contract, which is typically neurologic in origin. Some causes of detrusor areflexia include spinal cord injury, fractures, herniated disc, and infections. Damage to the detrusor muscle from chronic overdistention can lead fibrosis of the muscle with weakness in contraction of the muscle. This is often referred to as a myogenic bladder. A common cause of chronic bladder distension is benign prostatic hypertrophy in males and less commonly severe pelvic organ prolapse in females. Whether the issue is of nerve or muscle origin, they both can lead to poor emptying ability. A subset of women may have detrusor overactivity with poor contractility, which can lead to overflow incontinence. This is common in the aging female population. Detrusor overactivity is often associated with urgency incontinence. Urgency incontinence is the sudden urge to urinate which may lead to leakage. Urgency incontinence is common in older women with other comorbid diseases. Treatment of the underlying disease is the most effective treatment. Usually, the first steps in treatment involve conservative options with lifestyle modifications, pelvic floor exercises, and bladder training. However, if these initial conservative therapies do not improve symptoms, there are other pharmacologic and surgical therapies. The 2 medication classes commonly used are antimuscarinics such as oxybutynin and tolterodine or beta 3-adrenergic such as mirabegron. Antimuscarinics have side effects such as dry mouth, constipation, blurry vision, drowsiness and cognitive issues. Sacral nerve stimulation and Botox are other options. More invasive therapies include surgery with augmentation cystoplasty or detrusor myectomy which improves compliance of the bladder to limit or prevent upper tract damage due to high bladder pressures.[2][7][8]

Other Issues

Bladder cancer is one of the most common cancers of the urinary system. Patients present with painless hematuria with frequency, urgency, or dysuria in an older patient. Bladder cancer is diagnosed and staged by doing a cystoscopy with biopsy. The depth of invasion of the cancer is a key factor in determining therapy and prognosis. When cancer spreads to the submucosa or lamina propria, it is considered a T1 lesion. There are multiple therapies for T1 bladder cancers that include transurethral resection, intravesical therapy, and surveillance. However, when cancer invades past the submucosa to the detrusor muscle, it will be considered a T2 lesion. These are considered muscle-invasive bladder cancer. This is a very important distinction when it comes to therapies because T2 lesions have an increased risk of nodal and distant metastasis. Thus, when cancer invades the detrusor muscle, the standard of therapy is the removal of the urinary bladder (radical cystectomy) and divert the urine. Urinary diversion involves the creation of a bowel conduit or neobladder by harvesting a bowel segment. Finally, T3 lesions are when tumor extends past the muscle into the perivesical fat, and T4 lesions occur when the tumor extends to nearby organs.[9]


  • Image 7085 Not availableImage 7085 Not available
    Image courtesy S Bhimji MD
Attributed To: Image courtesy S Bhimji MD

Interested in Participating?

We are looking for contributors to author, edit, and peer review our vast library of review articles and multiple choice questions. In as little as 2-3 hours you can make a significant contribution to your specialty. In return for a small amount of your time, you will receive free access to all content and you will be published as an author or editor in eBooks, apps, online CME/CE activities, and an online Learning Management System for students, teachers, and program directors that allows access to review materials in over 500 specialties.

Improve Content - Become an Author or Editor

This is an academic project designed to provide inexpensive peer-reviewed Apps, eBooks, and very soon an online CME/CE system to help students identify weaknesses and improve knowledge. We would like you to consider being an author or editor. Please click here to learn more. Thank you for you for your interest, the StatPearls Publishing Editorial Team.

Anatomy, Abdomen and Pelvis, Bladder Detrusor Muscle - Questions

Take a quiz of the questions on this article.

Take Quiz
Denervation of the detrusor muscle would severely hinder emptying of the bladder. Which of the following supplies innervation to the detrusor muscle?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following arteries does not supply the detrusor muscle?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
What is the innervation of the detrusor muscle?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
What type of incontinence is associated with detrusor muscle overactivity?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up
Which of the following is continuous with the detrusor muscle?



Click Your Answer Below


Would you like to access teaching points and more information on this topic?

Improve Content - Become an Author or Editor and get free access to the entire database, free eBooks, as well as free CME/CE as it becomes available. If interested, please click on "Sign Up" to register.

Purchase- Want immediate access to questions, answers, and teaching points? They can be purchased above at Apps and eBooks.


Sign Up

Anatomy, Abdomen and Pelvis, Bladder Detrusor Muscle - References

References

Abelson B,Sun D,Que L,Nebel RA,Baker D,Popiel P,Amundsen CL,Chai T,Close C,DiSanto M,Fraser MO,Kielb SJ,Kuchel G,Mueller ER,Palmer MH,Parker-Autry C,Wolfe AJ,Damaser MS, Sex differences in lower urinary tract biology and physiology. Biology of sex differences. 2018 Oct 22     [PubMed]
Fitz F,Sartori M,Girão MJ,Castro R, Pelvic floor muscle training for overactive bladder symptoms - A prospective study. Revista da Associacao Medica Brasileira (1992). 2017 Dec     [PubMed]
Andersson KE, On the Site and Mechanism of Action of β{sub}3{/sub}-Adrenoceptor Agonists in the Bladder. International neurourology journal. 2017 Mar 24     [PubMed]
Purves JT,Spruill L,Rovner E,Borisko E,McCants A,Mugo E,Wingard A,Trusk TC,Bacro T,Hughes FM Jr, A three dimensional nerve map of human bladder trigone. Neurourology and urodynamics. 2017 Apr     [PubMed]
Iguchi N,Malykhina AP,Wilcox DT, Early life voiding dysfunction leads to lower urinary tract dysfunction through alteration of muscarinic and purinergic signaling in the bladder. American journal of physiology. Renal physiology. 2018 Aug 8     [PubMed]
Yoshida M,Yamaguchi O, Detrusor Underactivity: The Current Concept of the Pathophysiology. Lower urinary tract symptoms. 2014 Sep     [PubMed]
Radadia KD,Farber NJ,Shinder B,Polotti CF,Milas LJ,Tunuguntla HSGR, Management of Postradical Prostatectomy Urinary Incontinence: A Review. Urology. 2018 Mar     [PubMed]
Aoki Y,Brown HW,Brubaker L,Cornu JN,Daly JO,Cartwright R, Urinary incontinence in women. Nature reviews. Disease primers. 2017 Jul 6     [PubMed]
El-Achkar A,Souhami L,Kassouf W, Bladder Preservation Therapy: Review of Literature and Future Directions of Trimodal Therapy. Current urology reports. 2018 Nov 3     [PubMed]

Disclaimer

The intent of StatPearls is to provide practice questions and explanations to assist you in identifying and resolving knowledge deficits. These questions and explanations are not intended to be a source of the knowledge base of all of medicine, nor is it intended to be a board or certification review of Physical Therapy. The authors or editors do not warrant the information is complete or accurate. The reader is encouraged to verify each answer and explanation in several references. All drug indications and dosages should be verified before administration.

StatPearls offers the most comprehensive database of free multiple-choice questions with explanations and short review chapters ever developed. This system helps physicians, medical students, dentists, nurses, pharmacists, and allied health professionals identify education deficits and learn new concepts. StatPearls is not a board or certification review system for Physical Therapy, it is a learning system that you can use to help improve your knowledge base of medicine for life-long learning. StatPearls will help you identify your weaknesses so that when you are ready to study for a board or certification exam in Physical Therapy, you will already be prepared.

Our content is updated continuously through a multi-step peer review process that will help you be prepared and review for a thorough knowledge of Physical Therapy. When it is time for the Physical Therapy board and certification exam, you will already be ready. Besides online study quizzes, we also publish our peer-reviewed content in eBooks and mobile Apps. We also offer inexpensive CME/CE, so our content can be used to attain education credits while you study Physical Therapy.