It has been reported that the lung is the second most common site of metastatic focus for almost 25–54% of malignancies developing elsewhere in the body  with colorectal, head and neck, and urological tumors having the highest frequencies . Throughout medical history, the emergence of pulmonary metastasectomy has been described as incidental and fortuitous dating back to 1927, when Tudor Edwards described a sublobar resection of a metastatic lower limb sarcoma , followed by the first cohort of 25 patients at Memorial Hospital undergoing pulmonary metastasectomy with either a solitary lung lesion or multiple metastases but confined to one lung with an unfortunate 10 out of 25 patients surviving more than five years .
Pulmonary metastasectomy is performed when; 1) the primary malignancy is controlled or controllable, 2) no extrapulmonary metastasis exists except in colon cancer when lung and liver metastasectomies can be achieved, 3) metastatic nodules are resectable without compromising pulmonary reserve, and 4) medical treatment that has lower morbidity was deemed unsuccessful .
The development of minimally invasive thoracic procedures began with Kaiser et al. describing the first VATS operation back in 1995 in suspicious lung lesions . In the year 2000, the da VINCI robot was approved by the American food and drug administration (FDA) for usage in the medical field . Yoshino el al. were the first to utilize the novel technique in thoracic surgery . The first reported case series of laparotomy trans-diaphragmatic approach (LTDA) for a combined procedure was by Dionigi et al. in 2006 using a 5 cm incision around the diaphragmatic hiatus, which was utilized to access the thoracic cavity for pulmonary metastasectomy in two of the three reported cases .
Mise et al. published a case series spanning the years of 2000 to 2013 of sixteen patients with colorectal cancer and synchronous lung and liver metastases who underwent LTDA via bilateral or right subcostal, inverted L, J-shaped, or diaphragmatic midline incisions. Authors did not state the length of the incisions made nor the timing of chest tube removal . A 10 cm diaphragmatic incision around the central tendon was reported by Lerut et al. to access the thoracic cavity in the process of liver and lung metastasectomies .
Twenty-eight patients who underwent laparoscopic transdiaphragmatic VATS procedures using two-port entry sites to access the thoracic cavity with curative intent due to various etiologies, were reported by Andrade et al. Authors did not report an exclusion criteria but recommended avoiding such procedure in patients with a body mass index (BMI) ≥ 35 kg/m2. In addition, they recommended avoiding the left transdiaphragmatic approach in relatively young patients or those who practice heavy lifting due to increased possibility of herniation .
A reverse trans-thoracic approach via thoracotomy incision, with intra-abdominal liver segment resection was described by Delis et al. Authors reported 5 patients with metastatic colorectal cancer, two of which developed pleural effusion . Possible contraindications for this approach include but are not limited to tenacious adhesions in the pleural space; inability to obtain or to tolerate mono-pulmonary ventilation; pulmonary hilar lesions; neoplastic infiltration of the thoracic wall and contaminated or infected abdominal entity .
All studies reported chest tube insertion before wound closure without emphasizing how long it remained inside the chest cavity and when it was removed. They also reported pulmonary complications, such as pneumonia, air-leak, atelectasis, and pleural effusion without a clear postoperative timeline [13, 15, 16].
In order to avoid phrenic nerve injury and possible diaphragmatic paralysis, an incision should start anteriorly just lateral to the pericardium extending circumferentially as far posteriorly as needed, keeping in mind that incision through the central tendon will provide only minimal exposure with a low chance of diaphragmatic paralysis. In case other types of incisions were to be attempted, meticulous care should be carried to avoid the anterolateral and posterolateral branches of the phrenic nerve.
In the cases reported in this series, we entered the thoracic cavity via a 3–4 cm incision in the antero-lateral muscular part of the diaphragm (Fig. 4), avoiding the phrenic nerve and its branches. A limitation of the transdiaphragmatic approach is its narrow visual field in the thoracic cavity; we overcame this obstacle by using the VATS technique for better visualization, which permitted the safe performance of adhesiolysis in one of our cases. We utilized pre-operative chest CT scan for localization of the anatomical locations of the nodules. Following lung lesion detection and identification, we placed a curved clamp distal to the lesion and then applied an endostapler to cur below the clamp to ensure negative margin (Fig. 3).
Based on meticulous literature review of reported procedural details, no description of dual ring wound protector use on the diaphragm opening, as reported in our series, to facilitate the introduction of the VATS instruments and to protect the diaphragm wound from being contaminated by the tumor was identified. In addition, this case series is the first to report chest tube removal on the first post-operative day. Even though we accessed the thoracic cavity via a small incision, we were able to achieve resection with negative margins in all of the three reported cases. Based on the Sniff test performed on patient two and three, after six and three months post-operatively respectively, no abnormality in diaphragm function was detected.
For postoperative follow up, we can assess the diaphragm for any dysfunction using diaphragmatic sonography. This method is considered the preferred modality in children and young adult . Dynamic magnetic resonance has been described but is not widely adopted . The optimal test by far is the fluoroscopic sniff test where functional radiographs are used to assess the diaphragmatic motion during inspiration and expiration (Fig. 5). In normal conditions, both hemidiaphragms should move downward, but in case of paralysis in one hemidiaphragms, paradoxical motion is seen. This is exaggerated to bilateral paradoxical movements when both hemidiaphragms are paralyzed and reduced to only a delay in movement in case of weakness .