From the Guidelines

Chronic urinary retention is a long-term condition, whereas acute urinary retention is a sudden and short-lived condition.

Duration: The primary difference between chronic and acute urinary retention is the duration of the condition. Acute urinary retention is a sudden onset condition that is short-lived and reversible, whereas chronic urinary retention is a long-term condition that persists over time 1.
Causes: Acute urinary retention can be caused by a variety of factors, including obstruction, infection, or medication side effects, whereas chronic urinary retention is often caused by underlying medical conditions, such as benign prostatic hyperplasia (BPH), neurogenic bladder, or urethral stricture 1.
Symptoms: The symptoms of acute and chronic urinary retention can also differ. Acute urinary retention often presents with sudden and severe symptoms, such as inability to urinate, pain, and discomfort, whereas chronic urinary retention may present with milder symptoms, such as weak urine flow, frequent urination, or urinary incontinence 1.
Treatment: The treatment for acute and chronic urinary retention also differs. Acute urinary retention often requires immediate medical attention and may involve procedures such as catheterization or surgery, whereas chronic urinary retention may be managed with medications, lifestyle changes, or other interventions 1.

Assessment: Assessment of urinary retention is crucial in determining the underlying cause and developing an effective treatment plan. This may involve repeated bladder scans or intermittent catheterizations to assess bladder residuals 1.
Treatment Options: Treatment options for urinary retention depend on the underlying cause and may include medications, such as alpha-blockers or anticholinergics, lifestyle changes, such as pelvic floor exercises or dietary modifications, or procedures, such as catheterization or surgery 1.

From the Research

Urinary retention is defined as the inability to void, and it can be classified into two main types: acute and chronic 2, 3.
Acute urinary retention (AUR) is usually easy to identify, as patients typically complain of hypogastric pain and anuria 2.
Chronic urinary retention (CUR) is often more difficult to identify, as it is often asymptomatic and linked to increased post-void residual urine (PVR) 2.

The causes of urinary retention can be intrinsic or extrinsic, obstructive or non-obstructive, and can affect the lower urinary tract 2, 4.
Management of urinary retention depends on the cause and can include conservative treatment, drug therapy, and surgery 2, 5, 4, 6.
Initial management of urinary retention involves assessment of urethral patency and prompt and complete bladder decompression by catheterization 5, 4, 6.

AUR is typically characterized by a sudden and painful inability to pass urine, while CUR is often asymptomatic and may be identified by increased PVR 2, 3.
The American Urological Association recommends that chronic urinary retention be defined as PVR volume greater than 300 mL measured on two separate occasions and persisting for at least six months 6.
Management of AUR often involves immediate treatment with bladder decompression, while management of CUR may involve a more gradual approach, including voiding trials and initiation of alpha blockers 5, 6.