Introduction

Pelvic inflammatory disease (PID) is an infection of the female reproductive system, primarily affecting the uterus, fallopian tubes, and ovaries. In most cases PID is caused by bacteria from sexually transmitted diseases. If PID remains untreated it can lead to serious health consequences, one of which is a tubo-ovarian abscess (TOA). Tubo-ovarian abscesses are pus filled sacs that can become life threatening if they rupture, potentially resulting in sepsis. Around 30% of people hospitalised with PID experience TOA as a complication.¹ TOA can normally be prevented by treating PID in early stages, close monitoring and follow ups.

Overview of pelvic inflammatory disease (PID)

Symptoms 

PID has no distinct and obvious symptoms. Most symptoms are mild and often consist of the following:

• Pelvis and lower tummy pain
• Discomfort during sex
• Pain when weeing
• Bleeding between periods and after sex
• Heavy and painful periods
• Discoloured or smelly discharge 

Causes

Around 10-15% of cases of chlamydia (Chlamydia trachomatis), gonorrhoea (Neisseria gonorrhoeae), or Mycoplasma genitalium will develop into PID.² In developed countries, the role of chlamydia in causing PID is increasing, whereas the role of gonorrhoea is decreasing.³ This is mostly attributed to the common asymptomatic presentation of chlamydia, especially in women, as individuals unknowingly transmit the bacteria amongst sexual partners. These pathogens would usually only infect the vagina and cervix, but if left untreated in the late stages of the condition,  the infection will enter the upper reproductive tract. However, in most cases the cause of PID remains unknown. This is because harmless microbiota from around the vagina can gain virulence, bypass the cervix, and enter the upper reproductive tract where it causes infection. This is more likely to happen if there has previously been damage to the cervix. (NHS)

The people most at risk of developing PID include those with:

• Multiple sexual partners
• A new sexual partner
• History of STDs
• History of PID
• Under the age of 25
• Started having sex young

Pathophysiology 

The endocervical canal usually acts as a barrier to protect the upper reproductive tract; however, entry of bacteria (e.g. from STIs) causes the breakdown of cells in the endocervical canal. This allows vaginal bacteria to infect the endometrium, followed by the fallopian tubes, and perinatal cavity etc. Retrograde menstruation (backflow of blood) can facilitate the movement of bacteria from endometrium to the fallopian tube.⁴ During ovulation, oestrogen levels are at their highest, which facilitates and enhances the attachment of chlamydia, or gonorrhoea to the lining.⁵ Women under the age tend to have high oestrogen levels, thus they tend to be at greatest risk. Invasion of these bacteria attracts cytokines and other inflammatory mediators creating inflammation. Inflammation results in scarring, adhesions, and obstruction of the fallopian tubes. Scarring and adhesions leads to loss of ciliated epithelial cells in the fallopian tube impairing egg transport, increasing infertility and likelihood of ectopic pregnancies. In addition, adhesions are known to cause greater pelvic pain.

Development of tubo-ovarian abscess (TOA)

Symptoms

Usually TOA manifests with the following symptoms:

• Fever 
• Lower abdominal pelvic pain
• Tender abdomen 
• Discoloured or smelly discharge 

Pathophysiology 

PID infections continue to attract inflammatory mediators, thereby creating a blockage in the fallopian tubes until the ovary and fallopian tubes become fused together. This adhesion can help localise the infection, and results in formation of a walled off cavity. The abscess is polymicrobial, meaning it is composed of aerobic, anaerobic, and facultative anaerobic microorganisms. Giving the abscess the ability to grow under all conditions.⁶ Unlike other abscesses which are confined to an organ, TOA forms between the fallopian tube and ovary.⁵ This means the eggs released from the ovary cannot be fertilised; this causes infertility unless reversed immediately.  In addition to PID it is also important to consider that TOA can originate from the local spread of infections from inflammatory diseases, for example in the bowel, intestine, or appendix.⁵ Or occasionally as a complication of a caesarean section, hysterectomy or tubal ligation.⁶

Risk factors 

There are several groups of people who are vulnerable to developing TOA. Many of these are the same as PID because it is the most frequent cause. Other risk factors to these are:

• Immunosuppression - those with ovarian endometriosis have been identified as an at risk group due to their inability to fight infections.⁷
• Intrauterine devices (IUD) - long term use of IUDs increases risk of TOA.⁸
• Chronic PID - the longer and more severe symptoms of PID the greater the likelihood of developing TOA
• History of PID or TOA - scarring and damage from previous infections predisposes individuals for future complications.

Prevention of PID and TOA

Preventing PID to begin with is the best way to avoid developing TOA. PID is contagious and can be sexually transmitted. Therefore to prevent catching PID the most important prevention strategy is practising safe sex, through the use of condoms or other physical barriers. If you have PID it is important to stop your partner/s from also contracting PID, and potentially TOA. Another way to prevent PID is routine screening for STIs in sexually active women as early detection is key for preventing development into PID. Douching should also be avoided because it upsets the normal vaginal microbiota. 

If you already have PID it can be safely managed to avoid spiralling into TOA. However, some people with PID are more likely to develop TOA. People are predisposed to developing TOA if:⁹

• They have has an IUD implantation for more than 5 years.
• Of an older age - PID is most common among women ages 15-25 but TOA is most prevalent in women ages 20-40.
• Have a high CRP and CA-125 levels in PID infection - CRP is an inflammatory marker, which when below >11.5mg/l is likely to develop into TOA, as well as elevated CA-125 levels (normally found in peritoneum and fallopian tubes). 
• Obtained PID from a Chlamydia trachomatis infection.

Hence, effective strategies to prevent PID developing into TOA include limiting the duration of IUD use, and preventing contracting chlamydia. Other risk factors cannot be prevented, like age and efficiency of the body's response to infection. 

Treatment

Efficient and effective treatment of PID is essential to prevent development of TOA. Treatment of PID in the early stages begins with antibiotics. Antibiotics courses should be followed strictly as recommended by a GP, and as soon as possible. A mixture of antibiotics might be prescribed since PID is not attributed to only one type of bacteria. Antibiotic tablets should be taken for 14 days and the full course of antibiotics needs to be taken, even if symptoms are improving. If there is a chance of pregnancy inform your physician as some antibiotics are not safe during pregnancy. Sometimes a follow up appointment will be arranged 3 days after beginning treatment for the doctor to assess effectiveness of antibiotics. If the symptoms have not improved a physician will advise further tests, monitoring and if you have an IUD it should be removed. All sexual partners within the last 6 months or the last sexual partners should be tested and treated if infected. (NHS)

If PID is not immediately treated, recurrent PID, long term pelvic pain, ectopic pregnancy, infertility, and TOA might occur. TOA may also be treated with antibiotics ( intravenously in severe cases) which is successful in 70% of cases,¹⁰ although sometimes laparoscopic surgery (keyhole surgery) is required to drain fluid away from the abscess. This is a non-invasive surgery whereby a needle is inserted and guided by an ultrasound to visualise the anatomy.¹⁰

Summary

PID is an infection of the female reproductive system, primarily caused by bacteria from sexually transmitted infections. If left untreated, PID can lead to serious complications, including TOA, which are pus-filled sacs in between the fallopian tubes and ovaries. TOA results from persistent infection and inflammation, leading to closure of the opening between the fallopian tube and ovary. Preventing PID through safe sex practices is the most important way to stop infection. If PID develops early diagnosis and treatment with antibiotics is crucial to stop development into TOA. If TOA develops it requires further antibiotics (sometimes given intravenously) and may require laparoscopic surgery to treat in some cases.